London ? A thick cloud of bees was sucked into the engine of a passenger plane en route to Portugal, forcing the airline to abandon the trip and grounding passengers for 11 hours, a company executive said Saturday.

David Skillicorn, managing director of Palmair, said the swarm was spotted off Britain’s Bournemouth coast shortly before the Boeing 737 left Thursday. “Some witnesses claimed there were around 20,000 bees,” he said.

“The pilot experienced an engine surge about an hour into the flight,” Skillicorn said. “He returned to Bournemouth and we found what appeared to be a large number of bees smeared inside the engine.”

Around 200 passengers were delayed while the company carried out repairs and eventually replaced the aircraft, Skillicorn said.