Master beekeeper Stephen Repasky tells KDKA-TV 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 says 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.
Repasky says it's likely there's a wild honeybee colony at the airport somewhere.
The beekeeper was called to remove the insects because they're a protected species that cannot legally be killed.