The Department of the Air Force announced a $4.5 billion agreement to increase annual B-21 production capacity by 25 percent, accelerating deliveries while maintaining cost and performance targets. Expected further delays to sixth generation fighter development are expected to increase interest in procuring the B-21 at a higher rate to compensate for the lack of peer level fighters to China. The possibility of acquiring substantially more than 100 B-21s has been discussed within the U.S. Air Force for several years. During the Cold War, the U.S. Air Force operated hundreds of strategic bombers. Today, however, the inventory consists of 18 B-2 stealth bombers, and around 45 B-1B and 76 B-52H bombers, many of which require extensive modernisation.