One man said the engine was on fire and several people smelled smoke. One hundred and 45 passengers on flight 77 are back safely, but remember smelling smoke in the cabin at 2,000 feet.
A replacement plane from Denver landed at SFO shortly after 5 p.m., about two hours its scheduled arrival.
The initial flight was interrupted by a bird strike shortly after takeoff at Denver around noon. An airline spokesperson says a bird was sucked into the right engine and whole United initially said the pilot's decision to turn around was a precautionary measure.
One of the passengers caught a picture of the damaged engine. Two other passengers from the Bay Area gave a dramatic account of the bird strike and its impact.
"We just cleared the edge of the runway and there was a bird that hit the top of the engine, part of the bird flew over the top of the engine, part to the bird was sucked into the engine and the engine made a grinding sound," said Gary Little, a passenger.
"I saw flames shooting out of the engine and you could smell it, and everyone was really calm. I was surprised, everyone was very calm, then there were a few more flames shooting out of the engine and the pilot just said, 'Prepare for landing'," said Rebecca Lynn, a Flight 77 passenger.
It landed 24 minutes after the initial takeoff.
Recently a pilot's calm skill saved 155 passengers on January 15, 2009, when a flock of birds took out both engines of a US Airways plane. Danville pilot Sully Sullenberger made the heroic landing on NY's Hudson River.
It appears another calm mid-air decision by a pilot landed this group of people safely. Flight 77 is stopping in SFO in route to Honolulu.