A Norwegian Air Airbus A340 jet that aborted an international flight spewed a substantial amount of fuel on a large area of Orlando International Airport during its emergency landing, which an aviation expert described as a rare and potentially dangerous occurrence.

The incident happened late Saturday night, triggered initially by warnings of a failed hydraulic pump. Federal authorities have since begun an investigation while airport officials are assessing costs for cleaning up runway and taxiway surfaces.

The Norwegian flight, using a 19-year-old leased aircraft, was well out across the Atlantic Ocean when it reversed course and returned to Florida. Passengers were on board for nearly five hours, or more than half the time they would otherwise have spent on a flight to London’s Gatwick airport.

The returning flight was met by emergency vehicles, and passengers were held on the plane for an hour. Portions of the airport tarmac were closed temporarily so that crews could remove the spilled fuel.

Judy Watson Tracy was on that flight and from a window on the plane’s right side photographed a fountain of jet fuel coming from the rear edge of the wing to the runway.

Charles Westbrooks, aeronautical science professor at Embry-Riddle Aeronautical University and a former airline pilot, said most pilots never experience having to dump fuel. Far more rare is spilling fuel at an airport, he said.

“It would not be done intentionally,” Westbrooks said. “I can think of no reason why anyone would do that on purpose.”

Neither Norwegian nor the company providing the leased Airbus 340 for the London flight, Hi-Fly of Portugal, would explain why the wide-body aircraft dumped fuel on the airport’s runways and taxiways.