I never tried to make photographs of the stars from a plane, but the problems I see are (independent from the camera being used):
- Shake and vibration
- Reflection though the windows
- filtering effect
So you might consider these tools:
- Get a gimble (unless you can get very short exposure times at rather low ISO)
- Try to avoid light between the windows and the lens (maybe wrapping some black cloth around, or the cited rubber lens hood
- If possible "shoot raw" and try to optimize the results afterwards
I did not have a chance to inspect the cockpit windows closely, but "passenger windows" typically have "double glass" with significant distance (like 3cm) in between, so there will be reflections (not to talk about scratches).
Furthermore at high altitude there frequently is condensation or ice on the side of the glass you cannot reach.
Also consider whether it has to be from the cockpit and with a smartphone:
Maybe get or lease some photo equipment and make a short holiday at some good locations, like on islands like La Palma or Hawaii (if money permits ;-)).
The other thing is why you want to take photos of the stars at all:
Maybe use an app like Stellarium an simply enjoy what you can see with your eyes ;-)