co-founder of Microsoft and the 48th richest person in the world. The revelation, on December 17, 2003, the same day as the program's first powered flight test, followed speculation that Allen was involved. Some commentators have drawn comparisons between the relative inexpense of the Tier One program and the high cost of the Space Shuttle program, though the technological difficulties of the two programs are completely different. SpaceShipOne, because it flies suborbitally, does not need to reach the high speeds of the Space Shuttle (Mach 3 vs. Mach 25), nor the same altitude ( suborbital vs. orbit). SpaceShipOne also does not carry the same crew (3 members vs. 7) or payload (negligible vs. 25 tons), and makes much shorter flights (a few minutes vs. several days). The SpaceShipOne program is a technical achievement more on a par with the X-15 than the Shuttle. Inflation adjusted comparisons of the SpaceShipOne program with that of the X-15 budget, indicate that the Tier One program cost 1/100th that of the X-15 program, although the three X-15 aircraft made almost 200 test flights in their entire test program, typically exploring hypersonic flight between mach 4-7. Only a few dozen X-15 flights specifically sought to reach peak altitudes rather than achieve top speeds, though only two flights ever reached altitudes near those achieved by SpaceShipOne. On the other hand, the Tier One project also paid for construction of the White Knight mothership within its budget, while NASA had nearly free use of a pre-existing USAF B-52 bomber modified to perform drop tests of experimental aircraft of many kinds (currently in use for PegasusXL launches). Publicity Tier One was initially developed secretly, as is Scaled Composites' policy with new programs. On April 18, 2003 the program was publicly announced, and SpaceShipOne and White Knight were demonstrated to the media at a rollout attended by between 550 and 600 people. Media interest was so intense that what had been intended as a Family and Friends Day on April 24, 2003 was turned into a second media day. Scaled Composites again courted publicity by announcing in advance the final test flight, SpaceShipOne flight 15P, intended to be the program's first spaceflight. About 11,000 people went to Mojave Spaceport to watch the flight, which was also televised. The flight was run as an airshow, with both the principal craft and the chase planes making takeoffs and landings in front