strange fare rules ?
 

Airline 'X', member of SkyTeam, is offering a full Y (Economy unrestricted) fare on a certain route, which comes with the following rule:

fl.flt application
the fare component must be on
one or more of the following
any 'X' flight operated by 'X'
any 'Y' flight operated by 'Y'
any 'Y' flight operated by 'Y1'
any 'Y' flight operated by 'Y2'
(and this is all)

Airline 'Y' and its subsidiaries 'Y1' and 'Y2' are not SkyTeam, but Star Alliance members.

Strange or not? Please enlighten me :)

strange fare rules ?
 

Not strange at all.

strange fare rules ?
 

airlines have codeshares and other relationships outside of alliances all the time

strange fare rules ?
 

AF, for example, has a code share agreement with OS for flights between CDG and VIE.

Fare rules may provide for transport via any number of carriers pursuant either to bilateral relations or IATA rules without any regard to codeshare or alliance.

Not strange, and things like this also exist for booking classes other than full Y.

Thanks.
I found it odd that no Skyteam "partner" airlines were included, although they do operate there (but the only direct flight is with airline 'X' and that is not a codeshare flight).