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
Lockheed Martin F-35 Lightning II for transonic roll-off (wing drop). The possible obsolescence of stealth technology was also criticized. The single-engined F-35 closely resembles the larger twin-engined Lockheed Martin F-22 Raptor, drawing design elements from its sibling. The exhaust duct design was inspired by the General Dynamics Model 200, proposed for a 1972 supersonic VTOL fighter requirement for the Sea Control Ship. Although several experimental designs have been developed since the 1960s, such as the unsuccessful Rockwell XFV-12, the F-35B is to be the first operational supersonic STOVL stealth fighter. Acquisition deputy to the assistant secretary of the Air Force, Lt. Gen. Mark D. "Shack"