The following units can be upgraded to Stealth Bomber:
Stealth Bombers can attack enemy land units (and sea units, but less effectively). When attacking they cause collateral damage. Stealth bombers are very difficult for enemy aircraft to intercept and shoot down.
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.