Originally Posted by durberville

A delay on the first ticket, being an international ticket, is subject to the Montreal Convention. Should your first flight delay cause you to miss the second ticket, you are protected for resulting losses, including but not limited to the purchase of a new ticket as needed. If the delay is caused by something outside the carrier's control, then Article 19 would not apply, or in any situation where the carrier "proves that it and its servants and agents took all measures that could reasonably be required to avoid the damage or that it was impossible for it or them to take such measures."