Delays in the Ares I development schedule due to budgetary pressures and unforeseen engineering and technical difficulties would have increased the gap between the end of the Space Shuttle program and the first operational flight of Ares I. Because the Constellation program was never allocated the funding originally projected, the total estimated cost to develop the Ares I through 2015 rose from $28 billion in 2006 to more than $40 billion in 2009. The Ares I-X project cost was $445 million.