Pilots aboard United Flight 863 declared an emergency a short time after taking off from SFO at 10:45 p.m., FAA spokesman Allen Kenitzer said.
One of four engines powering the Boeing 747-400 apparently failed, Kenitzer said.
The plane turned around and landed safely at SFO without further incident, he said.
Hundreds of passengers who were on the flight are expected to board another flight Sunday night.
KGO contributed to this story