In the 1960s, both the Russians and Europeans pursued the development of supersonic passenger aircraft. The Tupolev Tu-144 was the first in the air on Dec. 31, 1968, followed by the joint British-French Concorde SST on March 2, 1969. Boeing won the U.S. SST competition in 1966 and proceeded with development, reaching only the mockup stage. In 1971 Congress canceled the Boeing SST, citing environmental concerns.