Should you turn your phone off during a flight?

"All electronic devices must be switched off during take-off and landing." It's a familiar announcement to all who fly regularly.

And for those who ignore the order, cabin crew on commercial planes are quick to appear with a stern follow-up request.

But why do they even bother?

"The myth that mobile phones have an effect on the electronics of the plane is not true," says Professor Andreas Strohmayer from the University of Stuttgart's aircraft construction department.

So you shouldn't feel too bad if you don't turn yours off. However there is another reason for the phone ban.

"Smartphones are constantly looking for signals and that interferes with the radio in the cockpit," explains Strohmayer.

"That means the pilot has a constant crackling in his ear." In the worst case the pilot may not be able to hear something important over the radio.

"Airlines vary in their estimations of how much interference there is."

Many airlines just play it safe and ask that smartphones, and other electronic devices, be turned off for take-off and landing.

As far as technology goes, experts say that it's sufficient to turn on airplane mode - which several airlines now allow.

"If airlines demand that you turn your device off completely, it's probably just because it makes it easier for them to check," says Strohmayer.

All the same, he says: "Generally you should listen to the instructions the airline gives you."

Because at the end of the day, they're in charge while you're their guest.