How are "charter" and "passenger" flights defined in the AIDX standard?
I know this question is 3 years out of date, but I thought I'd answer anyway. My answer is only applicable to Aviation Info Data Exchange (AIDX) schema 16.1.

As far as I know, there is actually no item in the format specifying the type of flight. But most systems I've come across have some coupled business logic that will make an AIDX request with the form of SheduleRQ and push this to a database. 
If the flight isn't in the database it will make a further PublicStatus request to determine if the aircraft info should be shown to the public. 

This might be a work around at the moment, but soon enough (2023-2025) AIDX will be integrated into AIDM and with all luck, unacknowledged requests will be a thing of the past.