Controller Thought He Never Cleared the Jet: NTSB Says Airliners Came Within 670 Feet at Boston Logan

An air traffic controller at Boston Logan International Airport had already cleared an American Airlines jet for takeoff and then convinced himself he had not, seconds before the plane rolled toward a runway where a Delta Air Lines flight was about to land, according to a preliminary report released this week by the National Transportation Safety Board.

The two jets, carrying a combined 318 passengers and crew, came within roughly 670 feet of each other on June 20 before the Delta crew broke off its landing. No one was hurt, and neither aircraft was damaged. But the sequence the NTSB laid out — a cleared takeoff, a false cockpit alarm, a controller reading a blank paper strip and a landing crew that saved the day on its own — is the kind of chain that federal investigators have spent the past two years warning about at busy U.S. airports.

The report puts the clearance at 11:33:43 a.m. Delta Flight 2351 had already been told it could land on Runway 33L, following a small plane onto the field. About a minute later, the local controller cleared American Airlines Flight 3161 for takeoff on Runway 27, which crosses 33L. The American crew began its roll, then stopped after roughly eight seconds when an error message appeared in the cockpit. The pilots checked their systems, decided the warning was spurious and resumed the takeoff about 23 seconds later — by which point the controller's attention had moved on.

Investigators wrote that the controller believed no takeoff clearance had been issued because the paper flight progress strip for the American flight was not marked. Controllers typically angle or annotate those strips to record clearances, and the missing mark became the controller's version of events until a surface conflict alert began sounding in the tower. In audio captured by the tower, the controller asked, "American 3161, where you going?" The reply from the cockpit was immediate: "You cleared us for takeoff."

By then it was the Delta crew doing the work. The pilots, on final approach, saw the American jet accelerating toward the intersection, judged that the runway would not be clear and executed a go-around, climbing away and circling before landing safely a few minutes later. The American crew watched the Delta jet break off and continued its departure.

The NTSB said the cockpit voice recording from at least one aircraft was overwritten before investigators could retrieve it, a recurring frustration in runway incursion cases and one reason the board has pushed for 25-hour recorders across the U.S. fleet. Flight data recorder information is still being analyzed. Preliminary reports do not assign blame; a probable cause finding typically takes one to two years, and the Federal Aviation Administration is conducting its own review of the tower's staffing and procedures that morning.