Thanks for all of the information. The "Fly America" is an interesting one. Some people may prefer it, but the U.S. government requires travelers on government business (at least in some cases -- I don't know if it's all) to fly a U.S. flag carrier on segments to and from U.S. soil. But code-shares are an exception, so it's OK to fly, for example, the Delta-coded, AF-operated flight IAD-CDG. (I wonder if that's the reason why Delta code-shares with AF on this flight? It wouldn't seem like a good candidate otherwise since IAD is not a hub for DL -- anyone connecting to CDG on DL would go through JFK, ATL, or CVG.)

Another stupid U.S. government rule that raises costs and lowers convenience for travelers. They would probably cite some vague "safety" or "security" rationale as the reason for the rule, but I'm sure that it's just protectionism.