what is this ad talking about? 2016 FREEBIRD, LS 103, Light Sport Aircraft, experimental amateur built. Issued GAS Airworthiness certificate Dec 2016. Always hangered. 20 hours on the airframe, 50 hp Rotax 503 engine, 2:1 reduction gear box, 4 blade Ultra prop. VFR day/night panel. Anti collision strobes/position lights. Panel mounted VHF comm. Two 6 gallon fuel tanks. Stits Poly Fiber fabric covered fuselage and tail surfaces,factory Dacron sailcloth covered wings and ailerons. Will consider trade for 4X4, Jeep, or BMW Any questions, please contact me. Not that I'm interested in the aircraft, just would like to know what a "GAS" airworthiness certificate is.