Originally Posted by
SkipperTheHooligan
I took a Y segment like this last year (ZYR-CDG). It was in a first-class carriage. I believe all tickets with an AF flight bumber are in the same, dedicated, 1st class carriage, and there would be no obvious benefit to the upgrade. I will double my sample tomorrow, but others will know much more.
ZYR-CDG is not TGV-Air. This is a different product. It replaces a defunct air link between CDG and BRU, with dedicated 1st class carriage and is called Air & Rail.
TGV-Air is a mix of TGV segment (with AF flight number) from or to cities around France mixed with a flight to or from CDG.
Other airlines offer this product as well.
I know it is confusing, hence my warning which you did not catch.