Written by JOHN WALTON

Do flight attendants know if you don’t put your phone on airplane mode?

Can cabin crew really tell if you’re still texting after the announcement to turn your phone off? Aviation journalist John Walton looks into whether there are phone detectors on planes — or not.

Does your flight attendant know if your phone is in flight mode or turned off?

As a rule, no. There’s no device that’s regularly installed on airplanes that can figure out how many phones, tablets, e-readers or other kinds of device are on in the cabin.

This whole thing is a big lie that dates back to when wifi wasn’t really normal on planes, and few aircraft had been tested to make sure that electronic devices didn’t interfere with their systems.

So if you’re a nervous flyer and hear it, please take heart: this is nothing to worry about.

But why do I have to turn them off in the first place?

The reason devices have to be turned to airplane mode or all the way off is that some of the onboard systems can be affected by interference from phones.

Interference is rare, and probably wouldn’t affect your flight, but aviation is an industry built on certainty, not probability.

The crew can estimate how many phones are in use

They may be able to turn on the onboard cellular connection and see how many devices autoconnect to it via the mobile network over 3G or 4G. This is largely restricted to longhaul planes.

And if you’re on one of the very latest planes, or a slightly older aircraft that’s just come out of having a new cabin put in, there may be another way for the crew to keep an eye on you: CCTV.

Wait, CCTV cameras? Really?

Yes, onboard CCTV cameras have been around for a while around the flight deck but recently they’ve been making their way into the cabin too.

You probably won’t spot the cameras: they’re often in a small, pinhole style, mounted in a panel at the top of the bulkhead walls. They’re also most often in business and first class cabins.

The new increased privacy for these deluxe seats mean that, at times, flight attendants can’t see everyone in the cabin from their cabin crew seats by the doors.

Why are they there?

Since regulations mean that the crew must be able to see into the cabin, enter the CCTV cameras. But even then, they can’t really know you’re online unless they see you tweeting or loading pages.

So you’re much more likely to get a tap on the shoulder from a flight attendant than to have your name or seat number blared out on the public address system.

Don’t worry that the plane will be affected because someone has left their device on.

And, relax

Just make sure yours — all of yours, including that e-reader and tablet — are in airplane mode or turned off, as directed.