I remember games like 1945 on the Commodore Amiga where you take control of World War II biplanes and blow the enemy out of the skies.
It's no surprise then that Altitude has been developed by two self confessed nostalgics for the good old days of computer games when everything was so much simpler. Altitude is a beautifully put together game and you can see that the developer has put a lot of time and attention into making it.
When you start Altitude, you have to perform a few practice runs to gain control of the plane. This is a bit annoying as I'd rather have the option to skip it but it is useful, if a bit easy. The controls are generally just the arrow keys with 'F' and 'D' firing your gun. Holding down the up arrow key ignites your afterburner.
Once this is done, you start to take on missions which basically involve blowing other planes out of the sky. The more missions you complete in Altitude, the bigger and better planes you unlock and the more interesting the scenarios you're placed in. You can play against a friend, other players online, or computer-generated opponents. There is quite a lot of loading and reloading throughout the game, which gets a bit tedious, but overall it's worth it.
Altitude does get a bit too crazy as you take on more and more planes and there is a bit too much repetition in the gameplay but overall its an excellent shoot-em-up.