The "real" reason for a policy is always more exciting. Watch:

The real reason you have to turn your phone off on a plane is so that you can't record the takeoff and landing. That way, if there's a crash, there's no evidence to dispute the airline's black box version of the story.

Pretty sick, no?

The people missing the point/satire of this comment are actually airline shills terrified that their secret has just been discovered.

The shills are everywhere, man. Who knows? You could even be a double-shill.

Nonsense. I've never heard that claim. And that policy was in place long before smartphones came along.

That's completely bogus. You only need to turn off the broadcasting it does, and even that was declared unnecessary by the FAA recently(iirc). You can record the takeoff and landing all you want, as long as you aren't affecting other passengers.

Funny story: two years ago, back when anything electronic was banned during takeoff/landing, I was flying to Svalbard. If you don't know it, it's a very beautiful, very cold island north of Norway. During final approach, the sunset was so beautiful that the flight attendants went "ah, screw it" and turned on their phones to take pictures. Naturally everyone else did as well.

In airline accidents, the NTSB and first responders handle the black box recovery. The airline doesn't touch the unit itself. The NTSB techs read the data and CVR audio.

Airlines are not allowed to comment on the investigation (including interpreting black box data) so the only official version is that of the NTSB.

I've never heard of an airline accident in the US where public or passenger video (cellphone or otherwise) contradicted the black box data.

Tyler Durden is real, and he reads Hacker News!

What's the REAL reason credit card companies don't keep backups?

This policy is so widespread, and it has been the policy for so long, that I would be quite surprised were such a reason not to have leaked out by now.

People with clearances all know about this maintenance mode. None of them ever explain the error of my ways, when I discuss it with them.

Sorry for the late reply. I would be very surprised if iPhones and most Android phones had this "maintenance mode". There are many people that are very familiar with every aspect of the hardware and software. When you have access to the bootloader, kernel, OS and even the init process before the bootloader, there isn't really anywhere to hide such a thing.

This just seems like outdated and paranoid policy to me.