Super Cobra is a sidescrolling shooter, originally an arcade game from 1981, ported over to Atari XL in 1983.
Quite a good port too, smooth scrolling, crisp graphics. See gameplay from the Youtube video:
Some tips by last years champion GGN
make sure you take advantage of the fact that the chopper can also go right and left, especially on the later levels
shoot fuel tanks frequently
learn to time the bombs to hit ground targets you like
unlike the arcade, the tanks don't shoot at you
The game works on Atari XL/XE as well as emulators.
Working emulators are Altirra on Windows, Atari 800 on Linux and Atari800MacX on OS X. Start a one player game with F4 on Atari800MacX and F2 in Altirra.