The sheet of metal weighing 130 pounds (60 kilograms) plunged to the ground shortly after Air France Flight 111 took off from Shanghai headed for Paris on Monday, Boeing said.
No one was injured in the Boeing 777 incident.
“We’ve been working real closely with our customers and have provided guidance on how to make any maintenance required,” spokesman Chris Villiers told AFP.
“It does not affect the structural integrity of the landing gear nor the safety of the flight.”
He said Boeing was treating the incident “with utmost concern and urgency.”
The panel, which Villiers stressed was not part of the landing gear structure itself, is one of the parts that open and close as the landing gear deploys.
Boeing has issued a service bulletin to the fleet providing instructions on how to resolve the issue.
The problem has to do with the fasteners that hold the panel in place.
In a statement, Boeing said: “We have implemented the change for airplanes produced in our factories.”
More than 1,100 Boeing 777 aircraft are in service with dozens of airlines around the world.