After a review of both proposals, NASA selected the Bell 301 for further development, and a contract for further R&D was issued on 31 July 1973. Extensive engineering and testing took the next four years to complete the development of the aircraft. The first of two Bell XV-15s, tail number N702NA, first flew on 3 May 1977. After minimal flight tests at the Bell test facility, the aircraft was moved to Ames Research Center in Mountain View, California, where it was then mounted in the large Ames wind tunnel and tested extensively in various simulated flight environments.