NASA's vomit comet is a second-hand McDonnell Douglas C-9B Skytrain II, a hollowed-out airliner that can briefly create weightless conditions for the occupants. But NASA isn't the only one with toys: the ESA also maintains its own weightless training aircraft, a stripped-out Airbus A310.
In order to create brief periods of weightlessness, pilots climb, top out, and then dive at 50 degree angles. During the top-out, the forces on the pilots and passengers cancel each other out. The ESA uses it to conduct experiments in zero-gravity, as well as to train astronauts.
The scary all-white walls are thanks to the padding. The flipside to zero weightlessness at the top of the climb is crushing twice-normal gravity at the bottom. The padding helps make that face-melting experience a little more comfortable.