There are no direct flights operated by Spirit Airlines PEK Terminal to Beijing Capital International Airport (PEK). For foreign legs, you'll probably need other airlines if you're connecting with Spirit through PEK. PEK has three terminals: T1, which is used for domestic flights, T2, which is used for numerous foreign services, and T3, which is the largest and handles a substantial percentage of the flights. During your transfer, you should plan to use the free shuttle service to get between terminals and be ready for security and immigration procedures. https://www.airportsterminalslocation.com/spirit-airlines/spirit-airlines-pek-terminal-beijing-capital-international-airport/