I've taken a few hundred, hiring someone else to fly, in which case:
Brief the pilot to fly the aircraft (comply with steps, heights, turns within the AC capacity etc. and where a shot is missed, fly a circle and come on to it again.
That gives an understanding between photographer and pilot, so both can work to the best efficiency.
Open the window which will float up to 90 degrees as others have said.
Use as small camera, with a short wrist cable, hold on to it with both hands like grim death.
Use the front window surround as LH Hand support, turn the camera to face the direction of travel, angle it down and "fly on" to the shot. You'll get great crisp shots with no prop or strut if you get it right.
There's a low pressure area close to the skin, so if you keep the camera in close it's a lot more relaxing, and you'll be further into the cabin, so no problems talking to the pilot.