The Boeing 747 left Singapore on Feb. 25 and landed at London's Heathrow Airport the next day, arriving only 15 minutes behind schedule, BA spokesman Jay Marritt said.
Three hours into the 14-hour flight, an oil pressure indicator showed there was a problem with one of the engines, which the captain shut down as a precaution, Marritt said. It was the captain's decision to continue with Flight 18, which was carrying 356 passengers, he added.
"It's still very safe to fly a 747 on three engines," Marritt said. "It is certified to do so."
Six days earlier,shortly after taking off from Los Angeles International Airport.
The pilot made an emergency landing in Manchester, England, about 160 miles short of London, because the Boeing 747 ran low on fuel after facing headwinds that were stronger than expected, the Federal Aviation Administration said.
The failed engine was later replaced in London, Marritt said. The aircraft then flew to Melbourne, Australia, before continuing to Singapore. It was on the return flight from Singapore, covering 6,765 miles, that the replacement engine failed, The Wall Street Journal reported.
"It was the No. 2 engine that failed but in totally different circumstances. It's one of those very strange coincidences," Marritt said.
The FAA and British aviation officials are investigating the Feb. 19 flight from Los Angeles to London to determine whether any regulations were violated.
"We are concerned," said Laura Brown, an FAA spokeswoman.
The decision not to return that flight after the engine lost power raised concerns about a new European Union law which requires European carriers to reimburse passengers for substantial delays. Those payouts can be hundreds of dollars per passenger.
After the first incident, the British Airways pilots' union issued a statement saying the new regulation could pressure pilots to take risks to save their employers money. British Airways denied that financial considerations were part of the crew's decision to continue the flight from Los Angeles.
U.S. officials said they have no evidence the airline's decision to continue on was influenced by the regulation.
"We would never compromise the safety of our passengers," said British Airways spokeswoman Diane Fung on Monday. "The plane is certified to fly on three engines. It is perfectly safe to do so. The pilots are trained for such situations."