You're mistaken, sir. Apple devices that have GPS receivers do not need data service (wifi or cellular) to get a GPS fix, although they can get a faster and more precise fix when wifi is turned on using aGPS. Apple devices turn off all the radios, including the GPS receivers, in Airplane mode (although the wifi can be turned on in Airplane mode). My understanding is that GPS receivers are not permitted to be used on an aircraft in flight if they aren't FAA certificated.

The built-in mapping app doesn't have the capability to download maps, so you need a third-party app if you want mapping capability when not connected to the Internet.