Question: AC3D is a 3D design program which has been available since which year, the software is used by designers for modeling 3D graphics for games and simulations - most notably it is used by the scenery creators at Laminar Research on X-Plane flight simulator produced by Laminar Research, and also ships with other software to build and customize aircraft and scenery?
Sentence (from "AC3D"): ac format has also been used in FlightGear for scenery objects and aircraft models.
Relevant evidence: No