Jetpac is a ZX Spectrum, VIC-20 and BBC Micro video game developed and released by Ultimate Play The Game in 1983. The game is the first in the Jetman series, and was the company's very first release. The game was written by Chris Stamper with graphics by Tim Stamper. Jetpac was one of the very few Spectrum games also available in ROM format for use with the Interface 2, allowing "instantaneous" loading of the game when the normal method of cassette loading could take several minutes.
In the game, Jetman has to first assemble his rocket (which comes in kit form), and then fill it with fuel before taking off to the next planet (where the procedure is broadly repeated). Along the way Jetman has to fend off the attention of intelligent (and not-so-intelligent) aliens, while making off with their valuable resources.
Source: Wikipedia, "Jetpac", available under the CC-BY-SA License.