Hi, I will be stopping over in Beijing for 2 days before travelling to North Korea for a week.

When returning to Beijing I will be flying straight to Chengdu for two days before flying to Hong Kong. My question is for the 2nd time I will be in China will I be able to get a transit visa as I arrive and leave from different airports? Or is the transit visa only allowed if you arrive and leave from the same airport within the 72 hours?