Your flight is delayed till the following day because of a mechanical problem. You find there is a flight with another airline the same evening so you book it, arriving home six hours late. You apply for reimbursement and compensation and are refused.
When I read a tale like this I always think what I would have done at the time, and what I would do now, and in this instance I'm really not sure. But this is a real life case in the Troubleshooter column in The Times today. Behind a paywall, I think, so here's the response (in part).
<<< Some airlines will agree to pay for you to travel on an alternative airline if you are delayed, but there is no guarantee. They should either arrange to take you home, or refund the flight you missed in full. British Airways has admitted as much and has now reimbursed Ian and paid compensation. A spokeswoman for BA says: “We have apologised to Mr Ganney for the delay to his flight and the genuine error with issuing EU compensation.” >>>
Note that there is no mention of "a gesture of goodwill". BA acknowledges a "genuine error", at least with regard to EU compensation. So I would read this as saying that if your airline cannot get you home within the three hours for a reason not outside their control, you are entitled to compensation irrespective of what you actually end up doing. But you are not necessarily entitled to reimbursement of any alternative travel costs (though you might well quote this as a precedent if BA were to refuse you).
Is that right?