I doubt Frontier will give any additional compensation.You made the decision to book Frontier and attempt to connect to an International flight on your own, probably to save money. Had you booked on the same airline or a code share partner then that airline would have had an obligation to get you to your final destination. If the issue was under Frontiers control (mechanical or crew issue) Frontier was only obligated to get you to your final destination on Frontier or refund your money. That they did more than that is commendable as they could have legitimately denied any compensation since you chose to take another carrier for your own reasons.
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