The Federal Aviation Administration has retired the airplane registration number used by pioneer aviator Amelia Earhart when she disappeared on a flight over the Pacific Ocean 50 years ago, officials said Monday.

FAA Administrator T. Allan McArtor said that number N16020 was retired at the request of Earhart's sister, Muriel Earhart Morrissey of West Medford, Mass.

"This number is never to be used by anyone ever again," the notation on the registration number reads. "Reserved for Amelia Earhart for infinity."

Earhart and her navigator, Fred Noonan, disappeared in the central Pacific in July 1937 on a round-the-world flight.

The disappearance has been the subject of speculation for years, with some theorizing that Earhart was captured and killed by the Japanese.

Most historians have said they believe that Earhart's plane ran out of fuel as she searched for Howland Island. Some have suggested that her maps were flawed. The plane was never found.

The registration number, displayed on the Lockheed L10 Electra, subsequently was reassigned and most recently was held by Continental Air Lines, which agreed to give it up.

"All I can say is that I'm very glad that this has taken place," said Morrissey when told of the FAA's action. "I think it's only fair that Amelia be honored in that fashion."

------------ THE FINAL FLIGHT --------------

Date: July 1-2, 1937

Destination: Howland Island, a tiny dot of land just north of the Equator and east of the International Date Line

Point of departure: Lae, New Guinea, 2,500 miles west of Howland

Crew: Amelia Earhart and navigator Fred Noonan

Aircraft: Twin-engine Lockheed Electra 10E

Background: Trip was one of the last legs on a round-the-world flight that began in Miami, in June 1937. Earhart and Noonan established radio contact with a Coast Guard vessel off Howland July 2, then disappeared. No trace of the plane or survivors was found.