Flames were reported coming out of one of the Boeing 747's engines at takeoff, airport officials said.
United Flight 897, scheduled to take off from Dulles International Airport at 12:23 p.m., dumped some of its fuel before its return in order to reduce the weight for landing.
Losing one of four engines does not create a serious safety concern, the FAA told CBS News correspondent Carter Yang.
Fire and rescue crews were standing by to meet the Boeing 747 which landed safely about 2 p.m., said Dulles International Airport spokeswoman Courtney Prebich.
A United spokesperson said their pilots took appropriate action in response to the lost engine in declaring an "amber" emergency and returning to Dulles. Airport officials had no immediate information about the cause of the flames.