Book excerpt: It has been called the most amazing and unbelievable aircraft of the 20th century. One look at the bat-like lines of the USAF's stealthy B-2 Spirit bomber quickly confirms this. But that futuristic shape has lineage back to the 1940s when the Northrop Company designed and built the B-35 and B-49 models - aircraft that closely resembled this 1990s flying wing version. Granted, the B-2 development program has had to endure a rocky road, but it is now here, and even though in smaller numbers than many desired, it will still present a formidable presence in the 21st century.