[ASSESS - Airborne Science Spacelab Experiments System Simulation.] Produced by NASA's Airborne Science Office, which is located at the Arnes Research Centre in San Francisco, this video outlines the use of experimental flights in the field of space science. Examples of such flights are given - namely, the 1965 990 Galileo 'chase' of a solar eclipse, the 1968 Lear jet-mounted infra-red telescope and the larger C141-mounted telescope flown in 1974. The way in which the ASSESS programme documents airborne science for Spacelab planners is explained. Footage is provided from two missions: a joint Russian/NASA airborne microwave radiometry lab, and the ESA/NASA Galileo 2 Spacelab simulator. The latter includes a very young Ulf Merbold.