I am in US, running iOS 15.5 and I tried US flights as well as international flights but it still doesn’t work for me.. so not sure if there is some privacy setting blocking it or if some feature we need to enable.

Worked for me with KL flight numbers, but only a few and they were all enroute to or from the US at the time of searching. So that may have something to do with it?

Edit: KL605 to SFO worked while typing (it's in the air now), KL1125 to Copenhagen did not work while typing but did show up after pressing search (it's in the air now). Similar for KL713 to Paramaribo worked after pressing search, while it's still on the ground.

I think it barely works outside of the US, but this is usual with most of the quick actions in Spotlight. Its kinda crazy all the extra options you get on Spotlight once you land in the USA.

Same in Brazil. Maybe it only works with flights in US.

It’s been reliably working for European flights for me for years. shrug

Does work for me for Turkish airline operators (I tried TK and PC)