I have shot air to air through windows with adequate results. (When you're shooting a jet from a pressurized turboprop, opening the window isn't really an option!) Just make sure the window is clean and you pick one with minimal distortions. Eliminate whatever light you can in the cabin soas to minimize the possibility of reflections.
Use a long lens, which will allow tight shots without getting too close, but not so long that your depth of field goes to nothing.
Avoid autofocus. Avoid auto exposure.
Avoid "flat light" days -- ie solid overcast. Also try to avoid harsh direct midday sun.
To get the solid propeller disc, the shutter speed should equal the RPM divided 60, divided by the number of propeller blades. E.g., 2400 rpm divided by 60 equals 40, divided by a 2 blade prop equals 20, or 1/20th of a second. Faster than that shutter speed and you will get only a partial disk.
Have the photog, camera ship and subject aircraft all on a discreet radio frequency. The photog controls the mission. The camera ship flies straight and level with the subject maneuvering around it according to the photog's instructions. Any camera ship maneuvers (for airspace, background, light angles etc) are requested by the camera ship pilot and commanded by the photog. Subject aircraft increases distance prior to camera ship maneuver.
Photog MUST have transmit capability to subject airplane.
Any loss of visual contact, break off and rejoin.
All maneuvers, frequencies and scenarios prebriefed. If the camera ship pilot starts looking at the subject airplane and trying to maneuver for the photog without instructions (and this happens A LOT with inexperienced camera ship pilots), abort photo mission.