Demand for air travel fell dramatically after the September 11 attacks, and Boeing began publicizing Project Yellowstone to potential customers for the first time in February and March 2002.[2] Branson, an early supporter of the Sonic Cruiser, was openly skeptical of the aircraft's prospects by July 2002: "Unless more runways are built the Sonic Cruiser is going to struggle because airlines will not have the slots to use the aircraft."[25] None of the prospective operators prioritized improved aircraft speed in a meeting with Boeing held in October 2002.[3]