There are a number of cheap apps with the best one I have used being iPlane.mil
Quite straight forward, easy to learn and the quiz it gives you helps understanding. The cadets can just jump in and learn from trial & error.
However, whilst it took a little while to set up I was able to take screen shots of the main aircraft that I wanted to use and (here is the fun bit) -
Make an Aircraft Recognition 'top trump" card set. The cadets can can play straight away without knowing the aircraft but get an understanding of its abilities and characteristics (as well as learn the name and the shape)
Aircraft Guess who? which using two packs help cadets learn the unique features of that aircraft. Both make a big change from the standing in front of the cadets doing a slide show.
Also, one thing I have come across is the Russian naming convention so Fox-bat = Jet fighter, Cub = Prop Cargo, Bear = Prop Bomber etc.
Once you get the aircraft sorted your then free to move on MIlitary Aircraft Systems i.e. Weapons Recognition