[teraflop]

Would that even be possible? I know I've never been able to get GPS to work reliably on any phone I've owned while on an airplane (even holding it up to the window), and presumably cell tower location wouldn't be available either above a certain altitude.

[GauntletWizard]

Edit: I am utterly wrong about my first point, the export controls don't kick in til 1,200mph or 59,000 feet; Both much faster and higher than standard commercial jetliners. [1]

GPS on your phone can't, by US law, work when you're in a plane. It is required that consumer GPS devices stop sending data when it is traveling over a certain speed, to prevent them from being repurposed as guidance systems for cruise missiles. Seriously.

You don't really need it, though. If you've got two or three people on the plane, the signal from when they all turn off airplane mode is a fairly good landing indicator. Takeoff is less steady; You're theoretically supposed to turn off your phone when they close the cabin door, but most people I know don't until they are actually taxiing down the jetway.

[1]https://en.wikipedia.org/wiki/CoCom#Legacy

[pmontra]

Out of curiosity, do the GPS chips stop working above a given speed or it's the smartphone sw that must stop reading from them to pass import controls? And what about GPS chips manufactured outside the US, put in phones sold outside the US by non american companies (I'd say the vast majority of the market), are they still subject to that limitation?

[exar0815]

I dont really know how it works, but its possible to circumvent, atleast some non-profit guys managed it: http://copenhagensuborbitals.com/gps-without-limits/