This raises another question:
I have never checked since my primary choice would be flying TATL "straight outta Frankfurt" (), so I check prices and book via the Delta website/app. Even if I end up having a first leg over to AMS for pricing, routing or even seat availability* reasons, I don't check if the same flight would have been cheaper on KL. (I avoid AF, as CDG is the worst hub airport in continental Europe that I have seen so far.) Would there usually be a price difference, potentially even being cheaper?

*) For me, there are only four seats on the A330-200 and -300 that I would accept in PS when I am flying solo. The rear two out of three rows, and in these rows the window seats. When I travel, I don't get up. I plop into the seat after boarding, and I literally sit there for 9 hours straight. And I don't want to have to get up for anyone, so window it is (unless I am traveling with someone I know who doesn't get up every five minutes). And, even though this may be an unpopular opinion around here, I think the bulkhead seats in PS are terrible. I am quite tall, and while they have decent "kneeroom", lacking a cut-out in the lower part of the bulkhead, I am not able to stretch my legs. That makes it extremely uncomfortable for me. And the "leg rest" doesn't help - No matter in what position I adjust it, my legs simply don't come in contact with it. I guess the upper part of my legs is just too long.