I have used cheapair.com for all of my flight purchases for years. I live internationally, buy international tickets all the time. No problems with cheapair paying with bitcoins.
I just bought a ticket for my girlfriend here in Thailand on kiwi.com because the only flights available on cheapair were $4k+ while the one I found on kiwi were $1500.
I actually bought the ticket a few weeks ago but when I went to print it out for her visa I saw that they never booked the flight sending her e-mails about verifying my payment.
I booked it again. I had to send them a copy of my passport, then a selfie. Then they e-mailed me with a phone number to call. I called the number and they verified more information, and now I have to wait for a third party service to get back to me to see if I'm ever so lucky to have the transaction go through.
I hate when I go from bitcoin back into the stone age of legacy finance. Everyone needs to just catch up already.
The difference is that you only pay once when using btc payment, while when you use credit card to pay, you have to use another account to return the money to the bank issued the credit card for you. And the special thing here is that when you pay by credit card you pay extra for your payment.