Its up to $3M a day.

Most credit card purchases can be disputed and get a chargeback up to 60 days after purchase. So the credit card servicer isn't going to wait in line after liquidation to get their money back from
Spirit since the bondholders are first priority for $2.1B. They want to make sure that if Spirit stops flying, that they have the cash in their possession to refund to the passengers.

This is why Spirit pulled the BK approved financing. Doing this put Spirit into junk bond territory.

Moody's Cuts Spirit Airlines Debt to Junk