The real reason is that the signals generated by your radio receiver (yes, it generates signals as well as receives them) can interfere with the aeroplane’s navigation equipment.
In an article for ‘The Straight Dope’, published in 1987, Cecil Adams (who ran a similar, but far superior, column to this one) explained it far better than I could. He said,
“Most modern receivers use something called a “local oscillator,” which is sort of an internal transmitter. The oscillator generates signal A, which is mixed with the somewhat raw incoming signal B to produce nice, easy-to-work-with signal C. There’s usually some sort of shielding around the oscillator, but it’s not always effective and sometimes errant signals leak out to make life difficult for other radio equipment nearby. If the other equipment happens to be an aircraft navigation device, somebody could wind up digging furrows with a $25 million plow. So do your bit for air safety and bring a tape player instead.”
Of course, you can replace ‘tape player’ with ‘iPod’ and not lose anything in the discussion…Feasibly, you could replace ‘iPod’ with ‘smartphone’ and lose even less.
However, the oscillator isn’t always going to cause a major problem, in fact, 9 times out of 10 you’ll be fine, but is it really worth endangering the lives of every passenger aboard the plane just so you can catch up on the football results?
Any answer other than ‘no’ would be inhumanly monstrous. Unless, of course, its a penalty shootout…
Actually, I’m over-exaggerating somewhat, in fact, not even your mobile would be likely to cause that much damage. In theory it could, but the reality for phones being banned is a little bit less terrifying, as www.Wired.com’s Cliff Kuang explains:
“Sure, your mobile can interfere with avionics — in theory. But in practice, it’s far from likely. Cockpits and communications systems have been protected against electromagnetic meddling through safeguards like shielded wiring and support structures since the 1960s. So why the resistance? Part of it, naturally, comes from the call carriers. When phones ping for signals at 35,000 feet, they can hit hundreds of towers at once, necessitating complicated parsing of roaming agreements. Providers don’t want the hassle if they’re not being properly compensated, so the government has left the plane ban in place”.
So, essentially, it’s not worth the risk to use a radio receiver on a plane and you can’t make calls because it would be a bugger to regulate, as well as a logistical nightmare to deal with, for the phone companies. That’s about it, really.