Boeing did so because the company expected supersonic airliners, whose development was announced in the early 1960s, to render the 747 and other subsonic airliners obsolete, but that the demand for subsonic cargo aircraft would be robust into the future. The 747 in particular was expected to become obsolete after 400 were sold but it exceeded its critics' expectations with production passing the 1,000 mark in 1993. As of October 2008, 1,409 aircraft had been built, with 115 more in various configurations on order.
