Most companies don't have a homegrown business travel booking system, but NetJets Aviation is a bit unique. Its business is scheduling travel and moving people around. The company in the mid-1990s spent $20 million to build proprietary logistics software to handle requests from clients. NetJets then layered on corporate travel components for its own pilots and flight attendants. Hotel booking automation came online in 2006, followed last year by some commercial air booking functions. Ground transport may be next.