The Model 733, illustrated by Boeing illustrator Ralph McQuarrie, was the early version of the Boeing Supersonic Transport or SST. The sleek design featured the efficient variable-sweep wing, shown here in the supersonic position with its wings swept sharply back into the classic "arrow" form, and with wings in the swept forward position for better handling at lower speeds. The design followed more than eight years of continuous research on large supersonic transport types and was evolved from some 500 designs studied as the best suitable for transport needs in the 1970's. Principal structure was to be of titanium. The Boeing 733 could have carried from 150-227 passengers and be capable of nonstop flights of more than 4,000 miles (6400 km).