Grumman X-29 experimental aircraft built in 1984 by Grumman for NASA to test the concept of forward sweeping wings. The high lift-to-drag ratio of the wing design provides the plane with enhanced manoeuvrability at supersonic speeds (faster than sound). It is able to turn mid-air quickly and is much less likely to stall at high angles of attack. The main disadvantage of this design was the increased stress load on the wings. This lead the X-29 program to be terminated in 1991.