Originally Posted by rdfry
exactly this has been bogus for years.
Not according to the Airbus and Boeing engineers and executives I worked with on projects in this area - devices that generate EM radiation, including RF, on commercial aircraft. Both companies conduct many many tests on every aircraft model, both for new designs and old ones, to try to avoid future incidents.
Both companies have found issues with outside EMI affecting their aircrafts' systems, sometimes dangerously. The most common problem was interference with in-flight entertainment systems; that merely irritates some passengers. More serious issues were interference with air-to-ground communication, and interference with instrumentation and flight control systems. I can assure you that pilots have had issues during landing due to consumer electronics in use by passengers.
For some insight into how hard it is to test for problems, consider these machines are crammed with wiring of all sorts running though many places, including below and above the passenger areas. A particular device may interfere only when in use around the area of a single seat, or a dozen seats scattered seemingly at random throughout the aircraft. A device may interfere only when in a specific orientation. A device may interfere only after it has been damaged in use, altering its EMI characteristics (even though it still works). The device may only interfere when signals are being send over a specific bus - not everything is in constant use. Those are reasons why the guy who said 200 iPods are the same as 2 is wrong; and, given his job, should know better, unless he was quoted out of context.
Somene mentioned plugging into some onboard system. This involves a wire. Wires are basically antennae, and they both receive and transmit. Mouse cords, USB cables, etc. all generate potentially problematic noise.
The specific limitation on takeoff and landing is because those are the most dangerous times in flying. A malfunction then gives the crew very little time, just a few seconds, to solve the problem or work around it. Once you are at 30k+ feet, you have more time to get things sorted out, so the risk is less.
If you know what you are doing, you can consistently cause real issues on at least some models of commercial aircraft, using only items that you are allowed to carry on board (I'm not talkng about someone's iPhone).
Most of the time, the things people argue over in life have no safety consequences. Having and espousing an uninformed opinion is fairly harmless. I wish people would pause to think: Do I really know anything about this subject? and: Are people's lives possibly at risk? And when the answers are "No" and "Yes", just say nothing - keep your opinion to yourself. But people of course won't do that. The blog author showed extremely poor judgement.
On a practical level, though, the answer is different. Commercial flight is very safe, at least in most countries. People ignore the rules and nothing permanently bad happens on almost every flight, thousands of times a day. So the risk, although present, is very small.