Beijing airport rank 21 busiest aiport in traffic movement with 431,670 total movement in 2008. One total movement is landing/taking off of an airplane. So that means there are about 98 total movements in an hour assuming only 12 hrs of significant traffic a day. If there is 7 min lap between flights to and from Shanghai, that means about 1/5 of traffics a day are between Beijing and Shanghai. That is rather high.