These types of missiles have the advantage of not requiring the launching aircraft to illuminate the target with radar energy for the entire flight of the missile, and in fact do not require a radar lock to launch at all, only target tracking information. This gives the target less warning that a missile has been launched and also allows the launching aircraft to turn away once the missile is in its terminal homing phase or engage other aircraft. The very longest-range missiles like the Hughes (now Raytheon) AIM-54 Phoenix missile and Vympel manufactured R-33 (NATO designation AA-9 'Amos') use this technique also. Some variants of the Vympel R-27 use SARH for the initial guidance and then passive infra-red guidance for the final stage. This type of missile requires active guidance for a longer part of the flight than fire-and-forget missiles but will still guide to the target even if radar lock is broken in the crucial final seconds of the engagement and may be harder to spoof with chaff due to the dual-type guidance. Criticism The efficacy of BVR air-to-air missiles has been criticized. A 2005 paper by USAF officer Patrick Higby showed that BVR missiles fell short of expected performance, despite incurring great cost. Because such missiles required large radars, they made aircraft heavier and increased drag, increasing aircraft procurement and operating costs. Fighters with BVR tended to be less agile than previous ones. Fighter pilots have been reluctant to use BVR missiles at BVR range because of difficulty in distinguishing friends and foes. As a result, most BVR missiles are fired at visual range. Western airforces only scored 4 BVR kills out of 528 kills made during 1965–1982; most kills during that period were made with guns or WVR missiles (AIM-9 Sidewinder). The increased success rate of BVR combat during 1991 Gulf war may have significantly depended on other factors, such as assistance of AWACS, NCTR system of F-15Cs, as well as enemy incompetence. None of the Iraqi pilots took any evasive measures, either because of poor training or their radar warning receivers malfunctioned. One major issue with BVR is still unreliable IFF technology (Identification friend or foe). In 2015 United States Naval Air Forces commander Vice Adm. Mike Shoemaker cited the sensor fusion of the Fifth-generation jet fighter Lockheed Martin F-35 Lightning II as the way to "bring that long-range ID capability and then share that information"