Sidelined and Sideswiped: The 1990 Detroit Runway Collision
On the 3rd of December 1990, a Northwest Airlines Boeing 727 taking off from Detroit, Michigan, sideswiped a Northwest DC-9 that had strayed onto the runway. The 727’s wingtip sliced straight down the length of the DC-9’s cabin, killing eight people and sparking a blaze that forced the survivors to flee for their lives. Somehow, amid thick fog, two planes had ended up on the same runway at the same time. How could this have happened? Was it a mistake by one of the crews, or by the air traffic controller? As it turned out, there was plenty of blame to go around. But in trying to figure out how the DC-9 ended up on an active runway, investigators discovered that its pilots possessed an unfortunate combination of personalities that led to a dangerously imbalanced cockpit dynamic. When these pilots, who were already lost and confused, encountered a poorly designed taxiway intersection, the clock began to tick down toward disaster.
The third of December 1990 dawned cold and wet at Wayne County Airport, the main international gateway to the city of Detroit. A morning storm dumped several centimeters of snow, all but shutting down airport operations. By midday, the precipitation had ceased, but dense fog still prevented any planes from landing. Nevertheless, several planes that had been grounded in Detroit overnight were queuing to take off. Among them was Northwest Airlines flight 299, an aging Boeing 727 scheduled to take 146 passengers and eight crew from Detroit to Memphis, Tennessee. In command of the flight were Captain Bob Ouellette, First Officer Bill Hagedorn, and Flight Engineer Darren Owen; put together, they had more than 10,000 hours on the 727, and they made an efficient team.
Also preparing to depart Detroit that afternoon was another Northwest airplane, a McDonnell-Douglas DC-9 operating flight 1482 to Pittsburgh, Pennsylvania. The commander, 52-year-old Captain Bill Lovelace, was about to begin his first unsupervised flight back at Northwest after six years on medical leave for kidney stones. In fact, he was so new back on the job that he hadn’t even been issued his uniform yet. He had just finished retraining and was still getting used to the procedures that had changed during his absence; in light of this fact, he had spent extra time preparing before the flight to make sure everything went smoothly. Joining him in the cockpit was 43-year-old First Officer Jim Schifferns, a former Air Force pilot who had spent years as a captain on the B-52 Stratofortress and the T-38 Talon. He had retired in 1989 with the rank of Major and switched to a career flying civilian airliners. By December 1990, he had been with Northwest for seven months, and had only 185 hours on the DC-9. All Northwest pilots undergo a probationary period for their first year at the company during which they are evaluated by their captain after every flight, and Schifferns was anxious to make a good impression. When the two pilots met at the gate, Lovelace asked Schifferns whether he was familiar with Wayne County Airport, and he replied that he was. Lovelace was pleased to hear this, as he expected to need help navigating the airport’s complex network of taxiways. Little did he know that Schifferns was perhaps embellishing slightly: in truth, he wasn’t particularly familiar with the taxi procedures either.
While parked at the gate, Lovelace and Schifferns carried on a running conversation about their respective aviation backgrounds. At one point, Schifferns remarked, “See, that’s the one thing that I miss — I’ve always flown with an ejection seat. Used it twice.”
Captain Lovelace appeared impressed. “Yeah I bet that was — how — was that scary when you punched out?”
“I got shot down once over Southeast Asia, and uh…”
“Oh, is that right?” Lovelace asked.
“I didn’t have time to get scared,” said Schifferns.
“And then when I was flying T-38s one time, I had a fire, an engine fire. That was a simple procedure in that airplane because if they — if the fire was confirmed, bold face was: throttles closed, engine fire shutoff switch pull, if fire is confirmed, eject. And you could confirm it, you know, with rough EGT high, or high EGT, or fire lights, and in my case the tower controller said — my call sign that day was DAY-21 — “DAY-21, you are on fire, eject.” So my decision was made. Bam, I — ”
“Was this right after takeoff or something?”
“Right on takeoff, yeah.”
“Wow,” said Lovelace. He was clearly impressed, but in fact, he had been taken for a fool. The entire story was a lie — although he did fly T-38s, Schifferns had in fact never used an ejection seat.
Minutes later, he casually mentioned that he had received job offers from Delta, American Airlines, and Northwest, but chose Northwest because American didn’t pay enough. Lovelace then asked, “How long were you in the service?”
“Twenty years,” Schifferns replied.
“Yeah, I retired as a Lieutenant Colonel,” he said, nudging himself up a rank — apparently “Major” wasn’t good enough. Once again, Schifferns resorted to outright lying in order to impress his captain.
At 1:35, flight 1482 pushed back from the gate and prepared to taxi. Believing that Schifferns was more familiar with the airport layout, Lovelace deferred to him for taxi instructions. The controller had instructed them to taxi to runway 3C via taxiways Oscar 6 and Foxtrot, which would have been fairly simple in good weather. But amid dense fog at an unfamiliar airport, Schifferns was a lot less sure of the location of Oscar 6 than he seemed.
“Just kind of wind around here and Oscar six is gonna be just right around the corner here,” he said to Lovelace, not realizing that Oscar 6 was in fact dead ahead. Taxiing along the inner taxiway adjacent to the parking apron, the pilots struggled to find the painted centerline that would guide them onto Oscar 6.
Painted centerlines play a critical role in guiding pilots along the taxiways, especially in low visibility conditions. Branches off the centerline show where to turn at intersections and help keep the plane oriented in the right direction. By failing to follow the centerline, Lovelace and Schifferns made their job much harder. Apparently unsure of the location of Oscar 6, Schifferns and Lovelace waffled over which way to turn. Schifferns capped off the inconclusive argument by remarking, “Man, I can’t see shit out here.”
When the pilots finally found taxiway Oscar 6, they turned onto it too late, missing its centerline. Captain Lovelace asked a series of questions about where they were going and which way to turn, which Schifferns did his best to answer. By now, Lovelace had completely handed over command of the taxi process to his first officer.
Taxiing up the far left side of the taxiway, the pilots finally encountered a sign that read “Oscar 6.” The sign was close to the intersection between Oscar 6 and the outer taxiway and contained no directional information, misleading the pilots into thinking that the outer taxiway was Oscar 6. They mistakenly turned left, heading east onto the outer taxiway instead of southeast along Oscar 6.
At 1:39, the ground controller asked, “1482, what’s your position now?”
“We’re headed eastbound on Oscar six here,” Schifferns replied. If he had stopped for a moment to compare their heading with his map of the airport, he would have realized that it was impossible to taxi east on Oscar 6, which was oriented northwest/southeast. The controller also missed this clue and simply asked the crew to report crossing runway 9/27, which at that time was closed for snow removal.
At 1:40, still heading the wrong way along the outer taxiway, the pilots encountered a sign pointing to Oscar 5, which connects the inner and outer taxiways east of Oscar 6. Schifferns radioed the controller and said, “Okay, I think we might have missed Oscar six. See a sign here that says, uh, the arrow’s to Oscar five. Think we’re on Foxtrot now.”
This transmission made little sense. Taxiway Foxtrot is the extension of Oscar 6 on the other side of runway 9/27, which they had not yet crossed. First Officer Schifferns seemed to be trying to convince himself that he knew where they were, when he should have stopped to more carefully examine his map.
The ground controller radioed back, “Northwest 1482, uh, you just approach Oscar five and you are on the outer [taxiway].”
Up until that moment, Schifferns had believed they were on Oscar 6 or Foxtrot, but he immediately replied, “Yeah, that’s right,” as though he had known all along that they were on the Outer Taxiway.
Having figured out the location of the DC-9, the controller gave it a new set of instructions to get back on track. “Northwest 1482, continue to Oscar four then turn right on X-ray,” the ground controller said.
The new plan was for flight 1482 to turn right at a six-way intersection involving Oscar 4, X-ray, and the Outer Taxiway. In hindsight, this might not have been the best plan — the Oscar 4 intersection was known to be confusing even in good visibility. Its signage was poor and its centerlines were badly faded. Knowing none of this, Lovelace and Schifferns continued slowly forward through the fog toward Oscar 4. Behind them, Northwest flight 299 made the correct turn onto Oscar 6 and proceeded toward the head of the runway.
Inching down the Outer Taxiway, the pilots looked for signs marking Oscar 4. Lovelace seemed confused, repeatedly asking Schifferns to confirm where they were and what the controller wanted them to do. Neither they nor the controller realized that the Oscar 4 intersection suffered from a dangerous design flaw. By the time the Oscar 4 sign hove into view through the fog and the pilots began looking for Taxiway X-ray, the plane was already half way through the intersection, and the right turn onto X-ray was behind them! Instead of taking the hard right onto X-ray, paralleling runway 3C/21C, they took a softer right turn onto Oscar 4 itself, which angles across the intersection of runways 9/27 and 3C/21C.
As flight 1482 approached the intersection of the two runways, it encountered a yellow hold line painted on the taxiway, where they were compelled to stop until the ground controller had given them permission to enter the runway. But the pilots believed they were on Taxiway X-ray approaching runway 9/27, which the controller had in fact cleared them to cross. Edging toward the hold short line, Captain Lovelace asked, “When I cross this, which way do I go? Right?”
“Yeah,” said Schifferns. Had they actually been on X-ray crossing runway 9/27, they would have continued straight.
Lovelace wasn’t convinced. The runway didn’t look right for the closed 9.27. “This — this is the active runway here, isn’t it?” he asked.
“This is — should be nine and two-seven,” said Schiffern. “It is. Yeah, this is nine two-seven.”
For a moment, the pilots looked for a taxiway on the other side, but saw none. Just before entering the runway, Captain Lovelace stopped the plane and put on the parking brake.
“Give him a call and tell him that we can’t see nothing out here,” he said.
At that moment, the ground controller called the DC-9 and asked, “Northwest 1482, ground, say your position?”
“Uh, believe we’re at the intersection of X-ray and 9/27,” Schifferns replied with confidence. The controller again cleared them to cross runway 9/27, and Lovelace let off the parking brake. Schifferns never replied to Captain Lovelace’s order to inform the controller that they couldn’t see where they were going. At 1:43, the DC-9 cautiously edged through the intersection and turned right, heading up the active runway 3C in the wrong direction.
Around the same time, Northwest flight 299 arrived at the head of runway 3C. The ground controller handed the flight over to the tower controller, who cleared them for takeoff at 1:44. But the pilots weren’t quite done with their takeoff checklist, and they sat there at the runway threshold making a few final adjustments to the plane’s configuration. The fog seemed to be thickening, and they were anxious to leave.
“Boy, this is dog shit right now,” remarked First Officer Hagedorn. The official weather report from the control tower pinned the visibility at a quarter mile (400m), barely above the minimum allowed on takeoff.
At 1:45, with all the checks complete, Captain Ouellette accelerated the engines to takeoff thrust, and the 727 rumbled off down the runway into the ominous gray void. “Definitely not a quarter mile, but ah, at least they’re calling it,” Hagedorn said. Although they had their doubts about the visibility, they weren’t meteorologists — they trusted the control tower’s figures.
Meanwhile on the DC-9, Captain Lovelace spotted lights and surface markings that suggested they weren’t on a taxiway. “Now what runway is this?” he asked. “This is a runway!”
“Yeah, left turn over there,” said Schifferns. “Naw, that’s a runway too!”
Lovelace pulled off to the far left edge of the runway and brought the plane to a halt. “Tell him we’re out here, we’re stuck,” he said.
“That’s zero nine,” Schifferns insisted.
Several seconds later, Lovelace attempted to contact the controller himself, but he apparently used the wrong frequency. At 1:44 and 47 seconds, he finally got through to the ground controller and said, “Hey, ground, 1482, we’re out here and we’re stuck, can’t see anything out here.”
“Northwest 1482, just to verify, you are proceeding southbound on X-ray and you are across nine/two seven?”
“Uh, we’re not sure,” said Lovelace. “It’s so foggy out here — we’re completely stuck out here.”
“Okay, uh, are you on a taxiway or a runway?”
“We’re on a runway, we’re right by [Oscar] zero four.”
“Yeah, Northwest 1482, roger, are you clear of runway three center?”
Inside the cockpit, Schifferns interjected, “We’re on runway two one center,” referring to the northern half of the same runway.
“Yeah it looks like we’re on two one center here,” said Lovelace.
Someone on the DC-9 uttered an expletive. The controller replied, “Northwest 1482, you say you’re on two one center?”
“I believe we are, we’re not sure.”
“Yes we are,” Schifferns confirmed.
Suddenly realizing that the DC-9 had strayed onto an active runway, the ground controller exclaimed, “Northwest 1482, roger, if you are on two one center, exit that runway immediately, sir!”
Inside the control tower, the ground controller announced out loud that the DC-9 was lost and was possibly on the runway, prompting a mad scramble to prevent a collision. Upon hearing the warning, the tower supervisor stood up and shouted, “Stop all aircraft, stop all aircraft!” At that very moment, the 727 was barreling down the runway straight at the hapless DC-9. But the tower controller, mistakenly believing that the flight had already taken off, made no attempt to stop it.
On board the 727, the pilots accelerated through 80 knots, unaware of the danger. Then, at 1:45 and 39 seconds, the DC-9 materialized out of the fog with no warning whatsoever. Captain Ouellette barely had time to shout, “Oh, shit!”
At exactly the same time, both pilots of the DC-9 spotted the landing lights of the 727 headed straight for them. “Oh shit,” someone screamed, as First Officer Schifferns dove out of the way of the oncoming plane. The 727’s right wingtip slammed into the cockpit of the DC-9 just below window level, tearing out the first officer’s instrument panel and showering the pilots with the shattered pieces of the wingtip navigation light. Sparing Schifferns by a hair’s breadth, the wingtip tore straight backward through the galley bulkhead and into the passenger cabin, slicing the plane open like a knife from one end to the other. In a split second, the entire right side of the cabin peeled apart, sending shards of debris ricocheting down the aisle. The 727’s wing continued its path of destruction until it slammed into the DC-9’s right engine, tearing it out of its mountings The impact also ripped off the outermost four meters of the 727’s right wing, breaching the fuel tank and spraying fuel down the side of the DC-9. Then, as quickly as it had arrived, the 727 disappeared back into the fog.
On the 727, the pilots managed to maintain control of the plane despite the brutal collision. Captain Ouellette shouted “Abort,” and First Officer Hagedorn announced on the radio, “Northwest 299, aborting three center!”
“Northwest 299, roger, report clearing the runway,” the tower controller replied. “Do you have any problem?”
“Affirmative, there’s an aircraft on the runway and we struck his, uh, wing,” said Hagedorn. Flight 299 safely rolled to a stop several hundred meters beyond the site of the collision, every one of its 154 passengers and crew miraculously unscathed. The plane was not so lucky: its right wing had been torn to shreds, with all kinds of cables and wires hanging from the mangled scar where the wingtip used to be. A piece of the DC-9’s right wingtip had also become embedded in the right main landing gear door, and fuel was trickling out onto the runway.
As the controller informed flight 299 that fire trucks were on their way, flight attendants urged the shocked and bewildered passengers to remain in their seats. In the cockpit, the pilots confirmed that there was no fire and elected not to evacuate.
“We were cleared for takeoff, weren’t we?” asked Flight Engineer Owen.
“Yeah, and they even cleared the guy behind us into position and hold,” said Ouellette.
Meanwhile, a rescue vehicle asked on the tower frequency, “Okay, where’s the aircraft that struck one on center?”
“I assume he’s on the last third of runway three center there toward the departure end,” the controller replied.
As fire trucks rushed to help the 727, airport authorities remained unaware of the horror unfolding on board the stricken DC-9. The impact instantly killed three passengers sitting in window seats on the right side, including at least one who was decapitated. Several others had been severely injured by flying debris. To make matters worse, the spilled fuel at the tail quickly ignited into a raging fire that sent black smoke pouring into the cabin. People started shoving their way toward the exits even before the flight attendants managed to open them. At first, no one pulled the handles to deploy the escape slides, forcing passengers to jump down onto the runway; some suffered serious injuries in the process. In the cockpit, Captain Lovelace cut power to the remaining engine and headed for the exit, only to find it already jammed with people. Instead, he opened the side window and escaped from the cockpit using a rope, followed shortly thereafter by First Officer Schifferns. A flight attendant finally managed to get down from the plane and pulled the external release handle to deploy the escape slide at the forward left exit, but no one ever released the others. One flight attendant and a passenger attempted to leave through the DC-9’s unique tailcone exit, but when they tried to release the tailcone, the handle broke. As the passenger struggled with the handle, both were overcome by noxious smoke and died on the spot. Three other passengers also failed to make it out of the plane, of whom two died from smoke inhalation and one from burning. By the time firefighters managed to locate the DC-9, most of the passengers were already off, but rescue attempts continued. First Officer Schifferns tried to climb up the slide to re-enter the plane, fell down, and was restrained by a firefighter. A flight attendant placed three injured passengers in an empty police car, but she was unable to find its driver, so she commandeered the vehicle and drove off in search of an ambulance.
After about 15 minutes, the 146 passengers on the 727 disembarked via a set of air stairs and were returned to the terminal. Over at the DC-9, it took firefighters an hour to put out the blaze, which had consumed most of the roof and the cabin interior. In all, eight of the 44 people on board were killed, and 10 suffered serious injuries. Although the deaths were tragic, the outcome could easily have been much worse. In fact, the crash appeared to be a near exact repeat of the 1983 Madrid runway disaster, which took the lives of 93 people.
In the Madrid accident, a DC-9 became lost in fog and taxied the wrong way onto the active runway. A Boeing 727 on its takeoff roll crashed broadside into it, killing all 42 people on the DC-9 and 51 of the 93 on board the 727. The parallels were many — the same types of planes were involved, they took place on almost the same day of the year, they occurred under the same weather conditions, and the errors made by the DC-9s in both cases appeared similar. But while the far deadlier accident in Madrid remained partially unsolved due to the lack of a cockpit voice recorder on the DC-9, this case would be different: both planes were fully equipped with modern recorders, and both sets of pilots had survived. The National Transportation Safety Board quickly launched an investigation to find out exactly why the two planes ended up on the same runway at the same time.
A review of the DC-9’s cockpit voice recording and interviews with its pilots shed much light on the accident. They were a troubled pair from the beginning: a captain on his first unsupervised flight after six years on leave; and a first officer with a distinguished military record, still on his probationary period and keen to impress. First Officer Schifferns spent much of the time before departure regaling Captain Lovelace with his qualifications and career history, some of which he had apparently made up on the spot. There was certainly no reason for him to have done this; his record was fairly impressive even without any embellishment. But the most important half-truth Schifferns told that day was actually his assertion that he was familiar with procedures at Wayne County Airport. After the accident, he claimed that he meant he was familiar with procedures at the gate and during pushback, not the taxiway layout. However, instead of clarifying this once they were underway, he allowed Captain Lovelace to convince himself that Schifferns knew more than he actually did. This led to an almost complete role reversal within the cockpit of Northwest flight 1482 in which First Officer Schifferns effectively took command of the aircraft, giving orders to Captain Lovelace and answering his questions about the procedures. It was certainly proper for Lovelace to accept Schifferns’ offer of help, but he should have taken an active role in monitoring their progress rather than deferring completely to his first officer. And Schifferns should have recognized that he was overconfident and spent more time looking over the airport map with Lovelace rather than trying to maintain an illusion that he knew what he was doing.
Part of the underlying problem in the cockpit of the DC-9 was that neither pilot had undergone formal training in Crew Resource Management (CRM). Northwest was one of the last major US airlines to implement CRM, and by the time of the accident, it still had no comprehensive CRM training program. One of the key principles of CRM is a balanced distribution of the cockpit workload. In this case, a disproportionate burden fell on First Officer Schifferns, because he performed all the navigational tasks while Captain Lovelace did nothing more than steer the plane. A second set of eyes paying attention to the map could have prevented the accident. Additionally, CRM emphasizes the importance of an open cockpit where pilots are free to say “I don’t know” without repercussions. Had Schifferns received this training, he might have felt capable of admitting that he was confused about their location. Instead, he kept blindly taxiing into the fog, unable to accept that he didn’t know where he was going.
The poor communication in the cockpit was only part of the problem, however. To try to replicate what the pilots of the DC-9 might have seen when they made their second wrong turn, investigators taxied a DC-9 into the Oscar 4 intersection and observed the taxiway markings. Even in perfect visibility, the investigators were unable to agree on which signs referred to which taxiways! Not only was the sign designating Oscar 4 well past the turnoff onto Taxiway X-ray, it was unclear which way the sign for X-ray was actually pointing. Furthermore, some of the painted yellow centerlines were so faded that they couldn’t be seen even in good weather. The deficiencies of the Oscar 4 intersection made it apparent how the pilots of the DC-9 could have turned the wrong way. Furthermore, the runway centerline lighting had been mistakenly turned off and the runway edge lights were placed too far apart, which could have disguised the fact that flight 1482 was entering the active runway 3C/21C and not the closed runway 9/27 as the pilots initially believed.
NTSB investigators also interviewed the air traffic controllers to understand what part they might have played in the sequence of events. Wayne County Airport lacked ground radar that would have shown the controllers the exact positions of taxiing aircraft, so the controllers had no way of confirming a plane’s actual location during low visibility conditions. However, the ground controller did miss some opportunities to notice that something was wrong. When the DC-9 reported that it was taxiing east on Oscar 6, a physical impossibility, the controller could have realized that the pilots were in over their heads. Instead, he gave them a new route that took the plane through an intersection that the airport had previously assessed to be hazardous even under good visibility.
When the pilots finally told the ground controller that they might be on the runway, he did take immediate action to inform the other controllers of the situation. The supervisor, who was at work at her desk and not actively monitoring traffic, immediately made the correct call and ordered all planes to stop. But the tower controller didn’t warn the 727 because he thought it was already in the air — an assumption he based on the fact that over a minute had passed since he cleared it for takeoff. He didn’t know that the pilots of the 727 were not ready for takeoff and had spent most of that minute finishing up their final checklist items. Had he looked at his radar screen, he would have seen that the 727 was not in fact in the air, but he did not. The NTSB was not able to determine whether his failure to issue a warning played any role in the accident, however, because all the accounts of what happened in the control tower were based on witness testimony, and an exact timeline could not be established. Investigators estimated that the tower controller could have had anywhere from ten seconds to zero seconds to stop the 727. 10 seconds might have been enough time to prevent the collision, but any less than that would probably have been insufficient. Additionally, the ground controller’s order to the DC-9 to “exit the runway immediately” came only seven seconds before the collision, not nearly enough time to move the plane out of the way.
Investigators also found that the official measurement of ¼ mile visibility was probably too generous. An off duty controller informally measured the visibility before the accident at 1/8 of a mile (200m), below the minimum allowable for takeoff. Controllers later testified that they didn’t use their visibility charts because they were familiar with what ¼ mile visibility looked like, but they also reported that objects and buildings less than ¼ of a mile from the tower could not be seen. Had they taken a more careful observation of the visibility, they might have found that it was too low for the 727 to take off safely, and the accident might not have happened. Additionally, the crew of the 727 independently assessed the visibility to be less than ¼ of a mile, but believed that they could take off as long as the official measurement was above the minimum and they could see the runway centerline. In hindsight, they should have trusted their gut — the official measurement was almost certainly wrong.
As a result of the accident, all involved parties made substantial safety improvements. Northwest Airlines introduced formal CRM training for all pilots, including emphasis on the admission of confusion, and revised its low visibility taxi procedures. Wayne County Airport changed the type of paint used for all taxiway markings; started a program to repaint all faded taxiway centerlines as soon as they were reported as deficient, rather than at a predetermined date; improved the runway edge lighting system; and completely removed the Oscar 4 taxiway by September 1991. McDonnell-Douglas improved the design of the DC-9 tailcone release mechanism to prevent the handle from breaking. The Federal Aviation Administration ramped up its efforts to prevent runway incursions, which included extensive investment in experimental systems that notify controllers whenever a plane enters a runway without permission. Multiple US airports accelerated their efforts to install ground radar systems. The NTSB also recommended that the FAA improve standards for taxiway signage, conduct a review of potentially hazardous intersections at airports around the country, and require the use of reflective paint for surface markings; and that controllers make greater use of progressive taxi instructions, among several other recommendations.
The Detroit runway collision was one of three accidents within a period of several years that prompted the mass rollout of technology meant to prevent runway incursions. Just three months later, in February 1991, a USAir Boeing 737 landed on top of a SkyWest Metroliner at Los Angeles International Airport, killing all 12 people on board the Metroliner and 23 of the 89 on board the 737. The NTSB found that the air traffic controller had forgotten to clear the Metroliner for takeoff before clearing the 737 to land on the same runway. And in 1996, A United Express Beechcraft 1900C landing in Quincy, Illinois collided with a private Beechcraft King Air taking off on a crossing runway, killing all 14 people on the two planes. In that case, the airport lacked a control tower, and the private pilot took off without informing nearby aircraft. All these accidents illustrated the urgency of installing ground radar and runway incursion alarms at US airports. By the 2000s, such systems were in widespread use, and in the years since they have proven extremely effective. The 1996 accident in Quincy was the last fatal runway collision in the US involving an airliner, and worldwide, no such collision has ever happened at an airport with a functioning runway incursion alarm system. However, there have been some close calls, which should serve as a reminder that maintaining this level of safety will always require constant vigilance from pilots and controllers alike.
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