Buying flights in Euro vs.$

The only way to be sure what fees you credit card company charges is to call and ask. There is usually a small (hidden) spread in the exchange rate to cover their cost of buying and selling foreign currencies, but the fee to be concerned about is the percentage most credit card companies now charge for foreign currency transactions. Think there were postings on that subject a few months ago. If you buy a ticket for Adria on a dollar site, there will likely be a larger (hidden) conversion spread than your credit card company charges plus the site's normal fees. As long as the percentage your credit card company charges is low, you're probably better off just buying in Euro directly from Adria. Adria will receive payment in Euro, so they won't add any hidden fees related to conversion. I've purchased directly from european airlines and received an e-ticket. Had no problems at check-in.

Thanks for the input. I'm trying to get a roundtrip flight from vienna to sarajevo. It's very expensive and looking at all flight options.

By the way, we flew from Vienna to Frankfurt on Adria Airlines. Very pleasant trip. The Adria aircraft was well maintained by Lufthansa. The flight was on time departing and arriving. I would fly with them again.

We have booked several times with RyanAir and Easyjet even with the small conversion charge, it is better $$ than other flights. A good website for inter-European flights is wegolo.com and then I go to the actual airline site.

I use skyscanner.com. It's a very good site with many search options.
You can compare both fares in EUR or USD by checking on xe.com and see in which currency would be better to pay.
Credit card companies charge some fees which come from the credit card bank issuer, the seller's bank and I think there are other small fees involved.
Asl your credit card company to break the fee down for you.