I have used GPS on tablet devices successfully when on the window seats on commercial aircrafts. The steps I take are:
1. Turn off AGPS or other forms of assistance. Use device only bare bones GPS.
2. Turn on GPS and let it get a fix on you at or close to the airport. This will preload the satellites' orbit information and make it quicker for the GPS to get a fix on you later. Turn the device off for boarding and take off as usual.
3. During cruise, turn the device on and hold it to the window for a few minutes. I use GPS Test app from Chartcross Limited which shows which (or whether any) satellites can be seen and their respective signal strengths. This app can also shows your altitude, ground speed and heading once it gets a lock. Once the GPS Test app shows that a successful lock is possible, I can switch to my navigation app with preloaded offline maps. I use MapFactor GPS Navigation Maps for this purpose.
4. Once a lock is achieved, it can be maintained even with the device away from the window. Note that when you exit the app or switch apps, the lock will be lost, and you will need to regain the lock by holding the device at the window.
I have not been able to get a lock from the centre aisle of a wide body plane. Strangely enough, my last flight was on a 787, and I was unsuccessful in getting a signal even with the device at the window. Maybe the dimmable windows on that plane interferes with the GPS signal?