The game takes place in a fictional 2007 where the Earth has been conquered by alien invaders. The player combats the occupation forces using vehicles under operation code named 'A-Jax' created to liberate the Earth. Game play is divided into two scrolling sections with two different vehicles: the first being a vertical scrolling section with the helicopter and a Rail scrolling stage with the jet/space fighter. The game spans eight stages and extends are set to 30,000 and a second at 150,000 points.
Source: Wikipedia, "Ajax (video game)", available under the CC-BY-SA License.
The game was also released under the name "Typhoon". This version was the same except that the stages were in a different order, starting with a fighter stage diving down upon a carrier, rather than a helicopter stage as in 'Ajax'. Typhoon was converted to a number of home formats.