For takeoff on short or improvised runways, rockets are mounted on fighter aircraft, which provide additional thrust and thus shorten the takeoff. These missiles are called JATO, an abbreviation for “Jet Assisted Take Off”.
The film shows the attachment of the JATO missiles to the belly of a Mirage, how the missile containers, rockets, fuses and electronics are assembled and tested.
Different recordings of launches show how the performance of the JATO rockets affects flight behavior.