(Image Credit: Stephen Repasky)

A Delta flight headed from Pittsburgh to New York was delayed Wednesday by thousands of bees on its wing.

A professional beekeeper was called in to remove the bees, ABC affiliate WTAE-TV in Pittsburgh reported. Master beekeeper Stephen Repasky said he was called when the bee swarm formed on the plane's wing as it refueled. He was called to remove the bees because they're a protected species that cannot legally be killed.

Delayed for about 20 minutes, fascinated passengers clicked cellphone pictures of Repasky at work, a Pittsburgh International Airport spokeswoman said.

Repasky said it was the forth time he has been called to the airport this year, so there's likely a honeybee colony nearby.

"When a colony of honeybees swarm, it's nature's way of dividing on a large scale," Repasky said. "So, the old queen takes off with half the colony and they go looking for a new place to set up residence."

Two swarms were removed in May and one in June, both from equipment but not planes, the airport spokeswoman said.

There have been two to three times as many bee rescues this year then is typical, Repasky said. He blamed the increase on the weather.