Two planes nearly collided in Boston after a false alarm and a controller forgot who he cleared for takeoff, the NTSB reports

Last month, two planes were on a collision course after a faulty warning light slowed takeoff and confused the air traffic controller. a preliminary report From the National Transportation Safety Board.

on June 20 Delta Air Lines Flight 2351 was cleared to land on runway 33L, followed by a small aircraft. A little more than a minute later and before the Delta plane touched down, American Airlines Flight 3161 was cleared to take off from the intersecting runway 27, the report said.

According to the report, the American Airbus A319 began rolling down the runway but stopped eight seconds later when the pilots received an error message in the cockpit. After double-checking their systems, they determined it was a false alarm and began accelerating off the runway towards the intersection 23 seconds later.

Pilots on the Delta Boeing 737 saw the possible collision and aborted their landing, circling the airport before finally touching down safely. When the American pilots saw the other plane retreating from them, they continued to take off.

The two jets, with a total of 318 people on board, were 670 feet apart at their closest point, the NTSB reported.

The controller told investigators he saw the American plane begin to roll, then turned his attention to the smaller plane to make sure it was out of the way of the incoming Delta flight. The NTSB said it recalled that when the anti-collision alarm went off in the tower, the Delta pilots had already taken evasive action and the controller was “confused” as the small plane moved out of the way. He told investigators that he normally kept the paper flight strips tilted that controllers used to track each plane as it cleared it for takeoff, but American’s strip was not tilted.

“American 3161, where are you going?” The controller can be heard asking this question in air traffic control audio recorded by ATC.com.

“You allowed us to take off,” the pilot replied.

In NTSB interviews, the pilots said neither plane received a collision warning in the cockpit.

The report stated that the taillights, which could have warned the American plane of an impending conflict, went off after the small plane landed and did not come on again until the Delta plane was on final approach.

The onboard cockpit voice recorders that record conversations between pilots only retain the most recent two hours of audio, and by the time the NTSB requested the black boxes, the audio of the close call had already been overwritten. Flight data recorders that record for longer periods of time collect information from onboard systems at the time of the incident and are currently being analyzed by the NTSB.

The board will determine the probable cause of the near-collision at the end of the investigation, which usually takes one to two years.

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