A generic retro-fit airbag is being developed for general aviation aircraft by the US manufacturer that supplies them as standard equipment in new aircraft.
Airbags made by AmSafe have been standard equipment on Cessna piston engine and Cirrus SR20/22 aircraft since 2005. AmSafe is developing a three-point restraint system with the airbag in the lap belt, and a detachable and retractable shoulder strap.
The airbag is set to deploy when the sensor detects a force at or above 6 Gs for approximately 50 milliseconds. After firing it deflates immediately to allow aircraft occupants to get out quickly after an accident.
Collected and summarized from the source below by Minh Pham