Maybe it's not a problem on airliners because they are better shielded, or just bigger, than a Skyhawk. But I can say first-hand that it is at least possible for a cellphone to interfere with an aviation radio.
Incidents involving interference from GPS, cell phones, etc. are recorded. The way people react when reading those reports is more interesting to me than the reports themselves. It's interesting how strong opinions are on this subject.
Maybe laptops (and planes) are much better than they were then, but I am amazed by the number of people who have persuaded themselves that there couldn't possibly be a problem so it is ok to ignore instructions to turn off their toys.
GPS devices are completely passive; how can they interfere?
(Unless you are talking about incoming GPS satellite signal. In which case -- dah, they've been out there for the last 40 years, the planes farrady cage structure should have accommodated this long ago, and it can be solved with strategically placed tin foil on the offending openings)
Interesting bit of trivia: the energy received from a GPS satellite is said to be roughly equivalent to a 40-watt light bulb on the other side of the continental US.
[0] https://en.wikipedia.org/wiki/Unintentional_radiator
[1] https://en.wikipedia.org/wiki/Superheterodyne_receiver#Inter...
Is there any reason to believe that a GPS unintentionally radiates more than (say) a walkman that has a radio? or a wristwatch that has a built in radio? Or that it should interfere with plane instruments more than the latter?
I'm not automatically discarding any report of interference, but I suspect a placebo effect is in play here, with people paying 10 times more attention to everything when they expect something should go wrong.
I'd like to know what makes avionics so special if it turns out that they are indeed very sensitive. Consumer, automotive, and industrial equipment has to shield against, filter out, and isolate all kinds of noise.
That should be "superstitious," not "suspicious." That post was made from a phone.
I figure that the way this works is something like this
* Flight instruments will have problems occasionally.
* People on planes always use electronic devices, but the flight crew here about it unless they specifically ask the stewardesses to look for people using electronic devices.
* The flight crew will ask the stewardesses to look if and only if there is interference.
Which means that if the flight crew are normal humans who have heard rumors that these devices cause interference, they will quickly be able to assemble what they regard as evidence for that view.
Reports have at times been as detailed as reporting that crew determined that a passenger's device caused interference with navigation equipment by observing the effect of repeatedly powering the device on and off. This isn't what the site is for, it's more generally about safety incidents.
The interesting thing about this to me is that it's not exactly inexplicable for devices to emit RF radiation when they shouldn't, or for equipment to not be shielded as well as it should, but engineering-minded people are often inclined to treat this like someone sighted a flying saucer.
edit: if that seems too much like an attack, I can tell you that I thought the whole thing was idiotic until I started digging into the reports and occasionally talking to people about the issue.