Q：If i fly from Hong Kong to Beijing and then fly out to Xian on the same day customs ,luggage and getting to gate? Would they be both in same terminal ..

A：When you arrive in Beijing from HK, you have to pass all of the courses for entering an international city, so at least one hour is needed. Then, for check-in flight at T2 to Xi'an, 30 minutes is enough. If you use T3, you should check in 45 minutes before the plane takes off . As for terminal transfer, the flights from HK to Beijing will land on at T2 and T3, both of which have the flights to Xi'an. So, you'd better check which airlines you will use.