A final report released by the US National Transportation Safety Board (NTSB) into an unresponsive controller incident that closed the Washington National airport control tower for approximately 30 minutes early on the morning of 23 March appears to raise questions as to whether two airlines that landed there during that period violated their own operating rules, a suggestion at least one of the airlines rejects.
Unusual conditions preceded the decisions: The lone controller in the tower cab that morning had fallen asleep for an estimated 24 minutes, leaving terminal radar approach controllers at a distant facility and the pilots themselves to figure out how to handle the radio silence.
The American Airlines Boeing 737-800 initially performed a go-around after not receiving a response or landing clearance when first contacting the tower, but ultimately decided to land at National, treating the airport as "uncontrolled" and following approach control's guidance. The United Airlines A320, arriving minutes later, did the same.
In a final report on the incident released 17 October, the NTSB cites the probable cause as "the tower controller's loss of consciousness induced by lack of sleep, fatigue resulting from working successive midnight shifts, and air traffic control scheduling practices".
Investigators had determined that the controller "had the necessary preconditions for the development of fatigue at the time of the event, specifically acute sleep loss in the 24 hours before the event and circadian disruption as a result of working the midnight shift".
The FAA in the wake of the incident made a series of changes, including scheduling of a second controller on the midnight shift at National and several other airports, ensuring nine hours scheduled "time off" following the working of a midnight shift and not allowing controllers to swap duty for a midnight shift while taking their "regular days off".
Regarding the pilots landing at an airport without an operational tower, the NTSB notes that both American and United have guidance in their company manuals that allows for landing at such a facility, providing the status of the airport is obtained before initiating an approach. Sources of that information can include arriving and departing aircraft, though terminal radar approach control is not specifically mentioned.
However the NTSB says the FAA-approved airline operations specifications for both airlines did not include National in a list of airports where the carriers are approved to land without an operating control tower.
An American spokeswoman tells Flightglobal that the FAA has "taken no action" against the airline, and in fact said the pilots "did what should have been done". She notes that operations specifications cover an airport in normal operation, which did not apply to National that morning. "The pilots will not be disciplined," the spokeswoman says. "They did what they were trained to do."