I don' t know if that applies to all situations. Last year I was travelling AA YUL-JFK-CDG and the flight to JFK went MX. While they wouldn' t rebook me on the a direct flight with AF the way Delta does they did put me on a BA flight via LHR. Agree with other posters that airlines should be forced to re-route on the next avail flight when the delay is there faults as sometimes agents are reluctant to do this, due to the effort involved. In the end, the cost would be minimal as all airlines have IROPS and they would simply be paying each other. If it turns out that one airline is spending more than the others then that airline would simply need to make a bigger effort to avoid having to buy full fare tickets on other carriers. And again, this should only be required on IROPS that are the airline' s fault, not MX or ATC.