A Southwest plane took off from a closed runway, forcing workers to evacuate the runway.

CNN
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Airport employees in Portland, Maine, were forced to clear the way when a Southwest Airlines plane took off on the morning of June 25 from a closed runway, according to air traffic control recordings.

Recordings made by LiveATC.net showed that air traffic controllers and pilots warned the crew of Southwest Flight 4805 several times to close the runway. The crash is now under investigation by the National Transportation Safety Board and the Federal Aviation Administration, and Southwest says it is communicating with both regulatory bodies.

For the past few months, the runway has been closed overnight for a taxiway construction project, reopening every morning at 5:45 a.m., according to the Port of Portland International. An observer said in the recordings that the tower was also closed for the night.

“There’s an airport vehicle,” a voice warned over the radio.

Another said: “Southwest heading to 29th, only to find out there is a vehicle on the runway and it is still closed.”

But the Southwest pilots apparently never heard the warnings. They were recorded communicating on a different radio frequency with regional air traffic controllers near Boston.

An air traffic controller in Boston later told Southwest that they departed three minutes before the runway reopened.

Boston Observer: “This runway is closed.”

Southwest Pilot: “I thought it opened at 45. There were no signs or anything.”

Controller: “We opened at :45, but you left at :42.”

Pilot: “That’s not what we’re offering, but that’s okay.”

The FAA told CNN that the runway was already closed at the time, and that “the airport vehicle exited the runway before the aircraft began takeoff.”

It is unclear how close the plane came to hitting the runway crew. The tower controller radioed the workers that he knew “you were on the runway and had to get out” because of the takeoff.

Southwest said the flight “continued safely to its destination” and referred questions to the NTSB, which said it is investigating and will release a preliminary report on the incident next month.

This is the latest in a series of safety incidents involving Southwest planes. Investigators are also probing recent Southwest flights that came dangerously close to crashing near Oklahoma City and one of the Hawaiian islands, as well as another plane crash in the Gulf of Mexico. Rare and unsafe swing in flight Known as the Dutch roll.