We initially planned for a nine-month mission, which we are roughly at now, but we will continue to extend the mission as circumstances allow. Keeping the X-37 in orbit will provide us with additional experimentation opportunities and allow us to extract the maximum value out of the mission.
We are learning new things about the vehicle every day, which makes the mission a very dynamic process.
Air Force says it’s extending mission of mysterious X-37B
Los Angeles Times
November 29, 2011
http://latimesblogs.latimes.com/money_co/2011/11/x37b-space-plane-air-force.html
X-37
Wikipedia
http://en.wikipedia.org/wiki/Boeing_X-37
US Air Force’s X37B ‘Secret Space Plane’ Marks Two Mysterious Months In Orbit
by Michael Rundle
Huffington Post UK
http://www.huffingtonpost.co.uk/2013/02/22/us-air-forces-x37b-secret_n_2739385.html
Eleven most expensive fighter jet aircraft in the world
https://kushima38.kagoyacloud.com/?p=14793