The transatlantic flight from Washington to Heathrow was surrounded by fire engines for more than 30 minutes as the Boeing 777 aircraft came to a halt at 10.30am.
It is not clear exactly what happened on Flight BA292 from Washington's Dulles International Airport, but it is not believed to be engine-related, British media reports said.
Photos appear to show three fire engines heading towards the aircraft on Friday morning - a routine response when a plane reports a problem.
A Heathrow spokesman said: "It was a full emergency but it's all clear. All the runways are open. The aircraft has been pulled back to its stand. It's just a technical issue."
More From This Section
A BA spokesman said: "The flight crew requested a priority landing as a precaution, and the aircraft landed safely.
"The safety of our customers and crew is always our main concern and our highly trained pilots will never compromise this," he added.
It comes two days after a pilot managed to avert potential disaster earlier this week when the engine of another BA plane caught fire before take-off at Las Vegas.
The US National Transportation Safety Board said parts of the high-pressure compressor component in the engine were found on the runway.
An initial examination of the British Airways jet found the left engine, fuselage and wing of the plane were substantially damaged in the fire.
The aircraft's flight data and cockpit voice recorders are now being examined by experts.
Pilot Chris Henkey was hailed as a hero after the plane's 157 passengers and 10 crew all escaped safely.