By 1971, however, Soviet studies determined the need for different types of fighters. The PFI program was supplemented with the "Perspektivnyy Lyogkiy Frontovoy Istrebitel" ("LPFI", or "Advanced Lightweight Tactical Fighter") program; the Soviet fighter force was planned to be approximately 33% PFI and 67% LPFI. PFI and LPFI paralleled the USAF's decision that created the "Lightweight Fighter" program and the General Dynamics F-16 Fighting Falcon and Northrop YF-17. The PFI fighter was assigned to Sukhoi, resulting in the Sukhoi Su-27, while the lightweight fighter went to Mikoyan. Detailed design work on the resultant Mikoyan "Product 9", designated "MiG-29A", began in 1974, with the first flight taking place on 6 October 1977. The pre-production aircraft was first spotted by United States reconnaissance satellites in November of that year; it was dubbed "Ram-L" because it was observed at the Zhukovsky flight test center near the town of Ramenskoye.