Hiller Ten99
 The Hiller Ten99 (also known as the Hiller 1099) was an American 1961 experimental helicopter created by Hiller Aircraft. The helicopter seated six and was similar to other helicopters by Hiller but featured a larger box-shaped cabin. It has four doors and a set of clamshell doors on its aft side. The aircraft was powered by a Pratt & Whitney Canada PT6 and in July 1961 was the first aircraft to have been powered solely by a PT6 engine.