I'm booking a a trip lasting more than 60 days to Europe. The fares on European carriers (AF, BA, others) center around $800, while all the US based carriers (UA, AA, etc.) are several hundred $$$ more. This is across enough dates in the future so I am pretty sure it's not an availability issue.

I believe there is a tariff rules that causes TATL rates to go up for stays greater than 30 days. Anyone know if this only applies to US carriers? If so, can someone book a flight operated by a US carrier (eg. AA) using a foreign carrier flight number (eg. BA) as a workaround?