The Skytrain is used to drop France's airborne: the Chasseurs-Paras. With no armament, it is compulsory to support the Skytrain with fighters to engage enemy planes and bombers to strafe ground targets and create a safe landing zone for the Chasseurs-Paras. Another thing is that the Skytrain is the slowest out of all transport planes making them extremely vulnerable against enemy AA fire, and also, it is the slowest plane of the whole game. So send out fighter escorts and destroy their AA units before sending the Chausseur-Paras to their targets.
The Skytrain is most likely based off the Potez 650 transport.
The Skytrain is the slowest and weakest transport plane in the game.