Maybe they're just on holiday.
According to an article in Reuters yesterday (granted, they don't specify the type of bee):
"A passenger plane was forced to land after flying into a swarm of British bees Thursday.
The Palmair Boeing 737, with 90 passengers on board, had to return to Bournemouth Airport in southern England shortly after take-off following an engine surge.
The pilot decided to abort the flight to Faro in Portugal and returned for safety checks. The plane's engine was thought to have become clogged with bees, the company said Friday.
Huge clouds of bees have been seen around Bournemouth over the past few days, a spokeswoman said."