Concurrent with the development of a stealth fighter, aeronautical engineers began to apply stealth technology to a full-scale bomber. The B-1B bomber, which went into service in 1986 as a replacement for the B-52, incorporated some of these innovations. The radar signature of the B-1B was reduced to a mere one percent that of the B-52 due to its low cross-section and its minimal use of radar-reflective, hard-edged surfaces. Soon after the B-1B entered service, the U.S. Air Force commissioned Northrop to develop a true stealth bomber as an eventual replacement. First revealed to the public in 1988, the B-2 stealth bomber uses a flying wing design similar in shape to the F-117A stealth fighter. The flying wing design reduces the profile of the B-2 by incorporating its engines into the body of the plane. The engine exhausts and intakes are shielded to prevent infrared tracking. The B-2 also makes use of curved surfaces and radar-absorbing materials to enhance its "invisibility", and make it far less detectable than the B-1B. As of the late 1980s, it was announced that 132 B-2's would be constructed, and would enter service sometime in the 1990s.