The Yakovlev Yak-1000 was a Soviet supersonic technology demonstrator intended to evaluate the aerodynamic layout and field performance of the cropped delta wing discussed in captured German documents in combination with the new Lyulka AL-5 turbojet. The tandem undercarriage proved to be unsatisfactory and there were serious flight stability problems related to the delta wing, enough so that it never flew after an accident during taxiing tests.