The GS2 have flight mode just for that reason my friend

Press and hold power then you can turn on flight mode.

 

Yes you can use the phone BUT it should be in flight mode.

• Long press the power button you shall get a pop up menu.
• Select Flight mode.
• Enjoy the flight.

Have a safe trip.

 

Do you mean rip a DVD to a PC then transfer that file to the phone and then watch it? If yes then absolutely yes.

SGS2 supports various formats playback and even HD 1080p playback.

 

recently come back from spain and watched mission impossible 4 on the way out and contraband on the way back on my s2.drag and drop and watch

 

Absolutely you can use the phone on the plane in flight mode. I normally listen to music and play gta 3.

 

On take off and landing it is normally requested, once in the air you can use it in flight mode.

 

you can use it, but i think flight mode isnt good enough for lift off and landing, then you have to turn it off.