It was distinguished from conventional airliners by its delta wing and high-subsonic cruising speed of up to Mach 0.98. Boeing first proposed it in 2001, but airlines generally preferred lower operating costs over higher speed. Boeing ended the Sonic Cruiser project in December 2002 and shifted to the slower (Mach 0.85), but more fuel-efficient 7E7 (later named 787 Dreamliner) airliner.