The sinking of ex-USS "Schenectady" as a test during Operation Resultant Fury in 2004 demonstrated that heavy bombers could successfully engage naval targets on their own. This led to the requirement for a new bomber that could survive against modern defenses. In 2004–06, the USAF Air Combat Command studied alternatives for a new bomber type aircraft to augment the current bomber fleet which now consists of largely 1970s era airframes, with a goal of having a fully operational aircraft on the ramp by 2018. Some speculation suggested that the next generation bomber might be hypersonic and unmanned. However, these were put to rest when US Air Force Major General Mark T. Matthews, head of ACC Plans and Programs stated that available technology indicates a manned subsonic bomber at a May 2007 Air Force Association sponsored event. He later stated that a manned subsonic bomber provides the "best value" to meet the required range and payload performance by 2018. The 2018 bomber was expected to serve as a stop-gap until the more advanced "2037 Bomber" entered service.