Does GPS work in Airplane Mode?
Yes. Your phone listens to satellites overhead and works out its own position without sending anything back. Airplane Mode switches off the radios that transmit: cellular, wifi and Bluetooth. Location can stay on, and GPS only ever receives.
Why Airplane Mode does not switch off GPS
Airplane Mode exists to stop your phone transmitting. Cellular, wifi and Bluetooth all broadcast, so they are disabled. GPS does not broadcast: satellites transmit, your phone receives. Turning off your transmitters has no effect on your ability to listen.
Your position keeps updating over an ocean with no cell tower for two thousand kilometres. Nothing has to reach the ground for your phone to know where it is.
How to turn it on before you fly
On both iOS and Android, Airplane Mode and Location are separate switches. Enable Airplane Mode as the crew asks, then check Location Services is still on. Most phones leave it on; a few need it re-enabled once after Airplane Mode goes on.
A window seat helps. GPS needs line of sight to satellites, and an aircraft fuselage is metal. Signal through a window is reliable; a middle seat in the centre section can be slower to acquire a fix.
What still will not work
Everything that needs the network stops. You cannot send your position to anyone, load a map tile you have not already downloaded, refresh arrival times from an airline feed, or see other aircraft. All of that is data moving over a network Airplane Mode has switched off.
Most flight apps go dark at cruise altitude because they fetch a position from a server rather than reading the satellites. SkyDot reads the satellites and draws on maps you downloaded at the gate, so it keeps working the whole way.
Questions
Does Airplane Mode turn off location?
No. Airplane Mode turns off the transmitting radios: cellular, wifi and Bluetooth. Location Services and the GPS receiver are a separate setting and can stay on.
Do I need wifi for GPS to work on a plane?
No. GPS is satellite positioning, not a network service. It needs no wifi, no mobile data and no inflight connection. You only need a network to download map tiles, which you can do on the ground before departure.
Will using GPS in flight drain my battery?
Less than you would expect. The receiver is doing the work and the transmitting radios are off, which is where most of the drain normally comes from. A long-haul flight on a full charge is comfortable.
Is it allowed to use GPS in Airplane Mode during a flight?
Airplane Mode is what airlines ask for, and it is the mode GPS reception works in. Your phone is receiving only and transmits nothing. Follow crew instructions on device use during taxi, takeoff and landing.