Incident Overview
On June 25, 2024, at approximately 0543 eastern daylight time, Southwest Airlines (SWA) flight 4805, a Boeing 737-79P registered as N7861J, departed from a closed runway at Portland International Jetport (PWM) in Portland, Maine. The flight continued without further incident to its intended destination, Baltimore/Washington International Thurgood Marshall Airport (BWI) in Baltimore, Maryland. The two flight crewmembers, three cabin crewmembers, and 131 passengers deplaned at the gate without any injuries. The flight was operated under Title 14 Code of Federal Regulations Part 121 as a scheduled domestic passenger flight.
Preflight and Dispatch
According to SWA, the dispatch release for the incident flight, titled "release -1," indicated a departure time of 0540, a 12-minute taxi out at PWM, and an arrival time at BWI of 0715. The flight crew reviewed a "Southwest Airlines Briefing" electronic weather packet generated at 0446. The packet included departure and destination weather and 32 Notices to Airmen (NOTAMs) for PWM, including a NOTAM indicating that runway 11/29 was closed until 0545 on the event date. The packet also contained a content page with a message that all flights departing from PWM before 0545 must call their dispatcher and receive a briefing from the Chief Pilot on call about departing from runway 18/36. The flight crew did not see the content page and did not call for a briefing.
Crew Actions
The flight crew arrived on time. The captain, serving as pilot flying, reviewed the aircraft logbook for open discrepancies, minimum equipment list items, and a maintenance release. The first officer (FO) conducted the exterior preflight and programmed navigation equipment. The crew used iPads to set up five flight-related applications, including Jeppesen FlightDeck Pro, WSi, and Comply 365. The captain accessed Comply 365 and noted that the PWM tower was closed until 0545, so Boston Air Route Traffic Control Center needed to be contacted for an instrument flight rules (IFR) clearance and void time. The application also indicated that morning departures should expect to use runway 29. The captain briefed this information to the FO and entered the departure, destination, and route into the flight management computer.
The crew reviewed NOTAMs and noted that runway 29 was closed on Saturdays and Sundays until 0545. The captain incorrectly assumed that any additional days for the runway closure would be in the same NOTAM; they did not see the separate NOTAM addressing the closure on other days of the week. The FO received performance weight and balance takeoff data via AeroData for runway 29. Normally, no takeoff data is received for a closed runway, only a message indicating unavailability due to closure. The crew did not brief the frequency they would use.
The flight pushed back from gate 4 after the FO announced intentions on UNICOM frequency 122.95. The FO made multiple calls to "Portland Traffic" regarding the planned taxi route to runway 29. Just before reaching the runway, the FO contacted Boston Center, advising they were number one for departure from runway 29. Boston Center gave a clearance void time with instructions to climb on runway heading to 4,000 feet. The FO again announced on UNICOM that the airplane would be turning onto runway 29 for departure. Both crewmembers observed a truck exit the runway while holding short; they confirmed it was clear. After a visual check, the crew verified the runway was clear and saw no equipment, markings, lighted "Xs," or other signs indicating closure. The flight departed runway 29 and continued to BWI uneventfully.
Airport Information
PWM is located about 2 miles west of Portland at an elevation of approximately 76 feet mean sea level. The airport has two paved runways: 11/29 (7,200 feet long by 150 feet wide) and 18/36. The PWM air traffic control tower operates from 0545 to 2200 daily. At the time of the incident, the tower was closed, but two certified professional controllers were in the tower and one was in the terminal radar approach control. The airport uses two frequencies for pilot communication when the tower is closed: the common traffic advisory frequency (CTAF) and UNICOM.
Investigation
The National Transportation Safety Board (NTSB) was notified by SWA on the day of the incident and began an investigation. Parties named include the Federal Aviation Administration, SWA, the Southwest Airlines Pilots Association, and the Boeing Company. NTSB specialists in air traffic control, operations, and flight data recorder analysis were assigned. The digital flight data recorder was removed from the aircraft and shipped to the NTSB's Vehicle Recorder Laboratory in Washington, DC, for analysis. Operations group interviews of the flight crew and dispatcher were conducted during the week of July 8, 2024. The investigation continues.