All 185 people aboard a Delta Air Lines plane had a lucky escape when the plane lost a panel on one of its wings mid-air during a flight from Orlando to Atlanta, US media reports said today.

"Crew members aboard Flight 2412 reported an access panel had come off the plane's wing while in flight," said Delta spokesman Anthony Black.

Flight 2412, with 179 passengers and six crew members, landed yesterday without incident at Atlanta's Hartsfield- Jackson International Airport, CNN reported.

The panel of the Boeing 757 came undone as the flight was in mid-air, leaving gears and wiring uncovered. As a precaution, the crew declared an emergency on approach, and the plane was towed to the gate after it landed, Black said.

He called the incident "highly unusual" and said, "the problems with the wing did not affect the plane's ability to fly or operable change in flight." Officials are inspecting the aircraft to determine a cause.

David Watterson, a passenger on the flight, was dozing off when he says he heard a big boom. He noticed a section of the plane's wing exposed and hydraulic fluid leaking.

"All the passengers were remarkably calm," he told ABC News. He said he did not feel any immediate danger, but it was "concerning to see a big chunk of the plane missing."