Hi, I have searched on the internet and found that from Islamabad to Urumqi there is no flight information after Sep.3, 2009, but before Sep. 3, the flight information is available. Maybe the airline hasn't published the flight information of that time.

And generally speaking, the round trip international tickets are cheaper than one–way tickets. You can submit the online booking form in the website as long as the flight information is published, may be in September.