IMPERIAL, Pa. – A beekeeper says he had to be called into gather up a swarm of thousands of bees that delayed a Delta Air Lines flight from Pittsburgh International Airport to New York.

Master beekeeper Stephen Repasky told KDKA-TV that he was called out on Wednesday when the bees gathered on the wing of the plan as crews were getting ready to fuel the plane.

Repasky said such swarms form when colonies become too large and the queen leaves half of her bees behind to find a new home. Some swarms can contain 25,000 to 30,000 bees.