In a parabolic flight, the aircraft is put into a suborbital trajectory that provides free-fall, or weightlessness. This is not a simulation. The weightless experience, other than duration, is exactly that experienced by astronauts on orbital missions. Several parabolas are provided per flight. A reduced gravity environment is obtained by flying a specially modified Airbus A300 through a series of parabolic maneuvers, which result in approximately 22 second periods of « 0g » acceleration (actually around 10^-2 g). Each parabola is initiated with a 1.8 g pull up and terminated with a 1.8 g pull out. A normal mission lasts two to three hours and consists of thirty parabolic maneuvers.

The Parabolic Maneuver (NOVESPACE Practical and Technical Information)

Starting from steady, level flight, the aircraft takes a 1.8 g load factor, nosing up to 45° and climbing to 23 000 feet over an interval of about 20 seconds. This is the entry pull-up phase.

Then the engine thrust is considerably reduced, to the point where it just overcomes the aerodynamic drag, and the pilot kills the lift. This transitory phase of "injection" separating the 1.8 g pull-up from the 0g parabola lasts fewer than 5 seconds.

The aircraft is then in microgravity phase for some 25 seconds. A symmetrical 1.8g pullout phase is then executed on the down side of the parabola to bring the aircraft back to its steady, level flight in about 20 seconds. There is an interval of two minutes between successive parabolas.