Any idea if there are international flights that charge extra for overweight people? I heard there is something called "customer of size" policy where they make fat people buy a second seat. It is being implement by at least one airline here in the US (Southwest) but I want to know if airlines like BA, Lufthansa or KLM are also implementing this.

Yes, you are correct about the US domestic airlines introducing paying more for "extra" weight, but I don't think the international airlines are doing this (yet).

Since weight is not a factor during reservation, I guess this becomes an issue during check in. You may best be prepared by calling the airline ahead or by holding extra money. But definitely not yet an issue with international airlines. And I don't think the domestic airlines are consistent in enforcing this revenue generating idea (they are too busy making money from fuel surcharge)

Thanks guys! I'm inviting my best friend over for the summer and she's over-weight. I think i'll just pay for an extra seat to avoid any hassles that might crop up even though she's assuring me that b4 the trip, she'll loose like 50lbs. I hope so!