This article 10 Secrets the Airlines Don’t Want You to Know has some good pointers on dealing with airlines when they mess up. For example:
Say ‘no’ to vouchers — you’re entitled to cold, hard cash
Do not settle for vouchers. They’re the airline equivalent of Geoffrey Dollars. If you’re bumped from a flight because it’s overbooked, the US Department of Transportation (DOT) has compensation rules of up to $1,300 in cash if the airline fails to rearrange plans within two hours of your flight. The airlines often offer passengers a travel voucher instead (like every time, let’s be real). They’re also required to tell you that you can get a check on the spot. It’s like your flight delay Miranda rights.
Aren’t airlines the worst sometimes?