Seven stranded workers had to be rescued by a Fire Department ladder truck.
Investigators said a jack was supposed to have been placed under the rear of the aircraft to stabilize it during unloading through a cargo door at the front of the World Cargo MD-11, airport spokeswoman Nancy Castles said.
``As soon as they took whatever it was out of the back of the plane, the weight shifted and the plane just went back on its tail,'' said Bob Collis, a fire spokesman.
The uninjured workers were rescued after about an hour by firefighters using a ladder truck, he said. Television footage showed a conveyor belt crushed under the plane's tail.
The accident involving the MD-11 World Airways cargo plane happened around 3:15 a.m. at the airport's cargo complex, away from regular airport traffic.
Collis said the same thing happened to another MD-11 in January 2002 in Sydney, Australia.
Airport officials may have to use a crane to right the plane, Collis said.
A message left at the Peachtree City, Ga.-based World Airways was not immediately returned Thursday.