Sweetman B. Aurora: The Pentagon's Secret Hypersonic Spyplane (Mil-Tech Series)

Motorbooks International, 1993. — 98 p. — ISBN: 0879387807.Why did the Pentagon retire the SR-71 spyplane in 1990? What has caused sonic booms over the California desert since 1991? What was the triangular craft spotted over the North Sea in 1989? In this groundbreaking book, journalist Bill Sweetman argues these mysteries can be traced to a U.S. spyplane called AURORA, the existence of which-denied by officials-lies buried in a secret military budget.