Flower is right...the "official" line is that AF will not board you. In reality you would probably get on out of Atlanta (coach as previously mentioned). You would ABSOLUTELY NOT get on coming back. In Paris, AF staff take a microscope to ID tickets. I have even heard them not allowing travel because of taxes not being calculated correctly by just a few dollars.

My recommendation would be to get the Global DL Pass and stick to DL. Officially the Global Interline pass is listed in rules as "Coach only", however as long as you are dressed right, you will automatically be put on the business class list...its just how it works at Delta. We do not look at the type of pass at checkin.

Happy travels!