For the record... flight attendants are NOT kidding when they tell passengers to turn off their cell phones prior to takeoff. After all, the phones can cause real problems for the plane's avionics -- at least, the captain of a Thomsonfly flight from England's Doncaster Airport on Monday believed so.

Passengers onboard the flight to Tenerife were told their flight would be delayed... while the pilot searched for his lost cell phone. The problem was due to the fact the phone had been switched on -- which is in violation of safety regulations.

As the captain searched for his lost phone -- and as luck would have it, the thing was switched to the "silent" ring function -- passengers were left waiting onboard the plane for an hour. They were then taken off the plane, and told they needed to wait for a replacement plane and crew.

"All mobile phones are required to be switched off during the flight for safety reasons," an airline spokesman told the BBC. "This is a very rare occurrence but as safety is always our priority the captain had no choice but to delay take-off until the phone was found."

That phone, incidentally, was later found onboard the plane -- after passengers had departed on the replacement aircraft.

FMI: www.thomsonfly.com