Originally Posted by
Phantasy
In this case, the only reason in forcing me to take a useless flight would be revenge.
What I like to know is in short: do airlines know what a passenger booked at the travel agency (when it contains flights from another airline with no alliance between these two)? Can the airline know I haven't checked in on a flight from an airline they have no alliance with?
The other reason for the airline to act would be to discourage others. As to whether either airline will know, that may be down to the communication between different GDS systems and the OTA system. From what you describe, I wouldn't risk it (and I have flown fuel dumped flights in the past).