Lockheed Martin SR-72 have the same range, with entry into service by 2030. The SR-72 follows the US Air Force's hypersonic road map for developing a hypersonic strike weapon by 2020, and a penetrating ISR aircraft by 2030. At the time of the concept's unveiling, Lockheed Martin had engaged in talks with government officials, but has not secured funding for the demonstrator or engine. On 13 November 2013, Air Force Chief of Staff General Mark Welsh revealed that the service was interested in the SR-72's hypersonic capabilities, but had not spoken with Lockheed Martin about the aircraft. Its high speed appeals to the
General Dynamics F-16 Fighting Falcon variants April 2007. In December 2006, the ROKAF placed a second production contract for T-50, T-50B, and TA-50 variants. The development of the FA-50 to replace the remaining old fighters is ongoing . Sources: USAF sheet, International Directory of Military Aircraft, Great Book, F-16 versions on F-16.net General Dynamics F-16 Fighting Falcon variants A large number of variants of the General Dynamics F-16 Fighting Falcon have been produced by General Dynamics, Lockheed Martin, and various licensed manufacturers. The details of the F-16 variants, along with major modification programs and derivative designs significantly influenced by the F-16, are described below. Two single-seat