A 787 Dreamliner caught fire at London Heathrow while a "technical issue" forced a second to return to a different British airport, sending stocks in the company plummeting.
The fire on the parked Ethiopian Airlines plane on Friday forced Heathrow, the world's busiest international passenger air hub, to shut down for 90 minutes but caused no injuries.
A Boeing spokesman said the US firm had personnel on the ground at the west London airport and was "working to fully understand and address this".
In a separate incident, engineers were inspecting a Florida-bound Thomson Airways Dreamliner which had to return to Manchester Airport in northwest England after take-off.
Boeing temporarily withdrew the Dreamliner from service earlier this year after concerns that batteries on board could cause fires, but has since rolled out modifications it said would ensure they were safe.
A Heathrow spokeswoman said the Ethiopian Airlines plane, named Queen of Sheba, was empty when the blaze was reported at around 1530 GMT.
Television images showed the Dreamliner surrounded by pools of foam, with three fire engines on the scene.
"Emergency services are currently dealing with the incident," the Heathrow spokeswoman said. "No one was on board so there were no casualties."
Heathrow announced at 1700 GMT (0300 AEST) that services were resuming, but warned passengers to expect delays.
Meanwhile, Britain's Thomson Airways said its Boeing 787 had landed safely at Manchester after experiencing a "technical issue" after take-off.
"Thomson Airways can confirm that flight TOM126 travelling from Manchester to Sanford, Florida, experienced a technical issue and the aircraft returned to Manchester Airport, as a precautionary measure," the airline said in a statement.
"Passengers have disembarked and our dedicated team of engineers are now inspecting the aircraft."
A spokesman for Manchester Airport, Britain's busiest outside London, confirmed that the plane was a Boeing 787 Dreamliner. It had landed safely about 1640 GMT he added.
Boeing's shares closed 4.7 per cent lower at $US101.87 in New York trading, clawing back from a dive of more than seven per cent.
The US Federal Aviation Administration said it was aware of the Heathrow fire. "We are in contact with Boeing as they assess the incident," a spokeswoman said.
A global grounding order on the Dreamliner was issued in January after lithium-ion batteries overheated on two different jets, with one of them catching fire while the aircraft was parked.
Boeing has not been able to identify the root cause of the problems - a source of major embarrassment to the aviation giant - but said its modifications would prevent the problems recurring.