I am travelling with a friend who works as cabin crew on a stand by flight

Hi, you are suggested to contact CVASC directly for more details. As I know, if you apply tourist L without invitation letter from a Chinese travel agency, then you have to provide round-trip ticket and hotel booking. You can have a try is the confirmation letter from the airline company acceptable for your application.

agree with the above. One thing needs to mention is that the hotel booking, unless the cabin crew company provide the hotel booking with your name on it, other than that, you need to book your hotel ticket. And the one you are applying for will be L type.