I don't know either. But, I could probably narrow it down to two or three. It may be a fine point. But, one doesn't have to be a particularly large donor to be on the team charter.
About all it would take is to be a tip in club member (about $125 a year), a season ticket holder, and be willing to pay a little extra than a trip would cost if one booked it themselves.
I doubt that there is a long waiting list for these trips with some people being denied while the seats go to the highest bidder.