American Airlines Inc. is investigating why a wide-body jet lost an exterior access panel shortly after it took off April 20 from Dallas/Fort Worth International Airport on its way to Paris.

The 3-foot by 6-foot panel, made of composite materials, apparently fell off the Boeing 767's belly as the aircraft was climbing past 10,000 feet.

In a message to American's pilots, managers said that the aircraft crew, which heard a noise and felt a brief vibration, could not identify the cause.

However, the crew, technicians and dispatch personnel determined it was safe to continue flying after no further problems were noted.

The airline discovered that the cover was missing when the airplane landed at Charles de Gaulle International Airport in Paris.

An American spokesman said the crew and passengers were never in danger.

An e-mail circulating among American employees criticizes the captain for not returning to D/FW Airport immediately.

“About 10 to 14 minutes after TO [takeoff], the crew in the back felt a very strong vibration from underneath, notified the cockpit and about six minutes or so later the crew in the back along with the paxs [passengers], heard a loud explosion,” the email said.

“Cockpit was notified and apparently, the Capt. deemed it not worth returning to DFW and continued onto CDG and well, surprise surprise” in Paris, the e-mail said, using the abbreviation for Charles de Gaulle.

Meanwhile, management pilots distributed a message Wednesday morning that defended the captain's decision to continue the flight, based on the situation and the information he had available.

“The captain treated the incident in a very professional manner and consulted with his fellow pilots, the cabin crew, dispatch, and AFW [Alliance Fort Worth] Tech on what the noise could have been,” two management pilots wrote.

“Based on his discussions with Dispatch and AFW Tech [the airline’s dispatchers and aircraft technicians at American’s Alliance Airport maintenance base] along with the fact there were no lights, system abnormalities or further noises or vibrations present, the captain decided to continue to CDG believing the noise might have been a cargo container shift,” they said.

The captain decided to keep flying since the airplane was 100,000 pounds overweight for landing at D/FW Airport, the managers wrote, “knowing that if anything recurred they could land before entering the oceanic portion of the flight.”

Off-duty pilots who were monitoring the cabin didn’t hear or feel any noises or unusual vibrations, and fuel burn “was normal,” they wrote.

“The facts of the matter are that this captain did exactly what we want our captains to do,” the managers wrote. “He did not make this decision in a vacuum; he consulted with his fellow crewmembers on the plane and with support staff on the ground.”

Based on spot market prices on that day, the 100,000 pounds of jet fuel would have been worth about $50,000.