Boeing 737-79P N7861J incident near Portland, Maine

Probable cause

The flight crew’s inadequate review of preflight information and the flight dispatcher’s noncompliance with company guidance requiring the placement of a flight lock, which resulted in the flight’s departure from a closed runway. Contributing to the incident were the flight crew’s use of an incorrect airport frequency and noncompliance with company predeparture briefing requirements, either of which could have identified the runway closure before departure.

NTSB analysis

Southwest Airlines (SWA) flight 4805, a Boeing 737-79P, N7861J, departed from a closed runway at Portland International Jetport (PWM), Portland, Maine. The flight continued without further incident to its intended destination.

The flight crew reported that before departure they reviewed the SWA weather packet which included the runway closure notice to airmen (NOTAMs). The captain stated that he reviewed a NOTAM describing weekend runway closures and incorrectly assumed that any additional closure periods would be contained within the same notice. This led the flight crew to believe the runway was not closed at the time of their departure.

The flight crew reported that a review of applications on their electronic flight bag (EFB) indicated departures should expect runway 29, and the flight crew was able to receive takeoff performance data. The first officer stated that, under normal circumstances, takeoff performance data would not be provided for a closed runway. Additionally, airport personnel had removed the lighted runway closure “X” markers before the airplane reached the runway, in anticipation of reopening the runway. Consequently, there was no visual indication at the time of departure that the runway was closed.

SWA guidance required dispatchers to place a flight lock on affected flights, preventing the release of takeoff performance data and requiring a briefing between the dispatcher, captain, and chief pilot before departure. Due to the nightly closure of PWM runway 11/29, the SWA dispatcher was required to place a flight lock until the required coordination occurred. However, the dispatcher did not place the required Flight Lock on the incident flight, and the flight crew was able to receive takeoff performance data for runway 29 and complete the departure without the required briefing. Had the flight lock been properly implemented, it would have prompted the required discussion and prevented the departure from the closed runway.

Lastly, the flight crew used the airport universal communication (UNICOM) frequency rather than the designated common traffic advisory frequency (CTAF) while operating at the uncontrolled airport. Airport operations personnel observed the airplane taxiing for departure and transmitted on CTAF that runway 29 remained closed and would reopen at 0545. Because the crew was not using the proper frequency, they did not receive or respond to this transmission.

Text from the NTSB. Open the NTSB docket for DCA24LA219 for the full record.