Delta Air Lines is investigating what caused a 4-foot-by-8-foot panel to fall off the wing of a Boeing 757 during a flight from Orlando, Florida, to Atlanta.

Flight 2412 landed safely in Atlanta about 7:30 p.m. local time yesterday after the pilot declared an emergency, Anthony Black, a Delta spokesman, said in an interview today. None of the 179 passengers or six crew members were injured.

The panel, roughly triangular in shape, was discovered missing from the top of the wing after the crew and others on board heard a noise during the flight, Black said. The missing panel “didn’t inhibit their ability to continue to operate the flight” on to Atlanta, he said.

How far into the flight the incident occurred wasn’t immediately clear, Black said. The aircraft left Orlando about 5:30 p.m.

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After landing, the plane was towed from the runway to a gate so passengers could exit, then moved to an aircraft hangar for the investigation.

The Atlanta-based airline operates 154 Boeing 757s among its main jet fleet of 743 aircraft.