Orbital space tourism has been expensive and limited, primarily offered by the Russian space agency until a halt in 2010; companies like Virgin Galactic and XCOR Aerospace are now emerging in the suborbital tourism market. Prices for flights to the International Space Station ranged from $20–40 million between 2001–2009, while Virgin Galactic plans to launch commercial flights in 2015 at $250,000 per seat. Earth, the densest terrestrial planet, formed about 4.54 billion years ago and completes 366.26 rotations during one orbit around the sun.