Hello
When you have two airlines in two different holdings, you can't sign an interline agreement between them, it is blocked, because the game's rules don't accept this
But when you buy an airline with a new holding and you already had an interline with this airline, the agreement is still valid
Users that don't know this point can play without knowing that the game's rules does not permit this situation
I suggest that, when a player becomes the owner of an airline, the system automatically checks if there are interline agreements between the new airline and the other owned by the same player and terminate any existing agreement with an automatic private message confirming this
See you