Pakistan International Airlines provides direct round-trip flights between Islamabad and Beijing. The flight from Islamabad to Beijing is available on every Thursday and Sunday and the return flights are available on every Monday and Friday.

China Southern Airlines has direct flight from Islamabad and Beijing and connecting flights from Beijing to Islamabad (transferring at Urumqi). The lowest airfare from Islamabad to Beijing on September 20 is CNY3,230 (excluding tax and fuel surcharge), and it is just for your reference!

For the lowest airfare, you would better consult some booking agencies because the international airfare always changes. Besides, you need to provide your exact travel dates.