Of course, when delays start compounding, the airline inevitably falls back on whichever one puts the least blame on them.

I forget the specifics of it, as it was over a decade ago, but I experienced a 4 hour MX delay. As the aircraft pulled away from the gate after the MX delay, a massive thunderstorm rolled through, costing us another 15 minutes. Of course, had it not been for the MX delay, we'd have gotten out before the weather caused a delay, and the weather delay was nothing compared to the MX delay, but when people were dealing with the problems caused by the delay, the airline treated it as if the weather was the reason for the misconnects.

The rule of thumb as I understand it is that when there are multiple reasons for different parts of a delay, the airline will always attribute the entire delay to whichever reason puts the least liability on them, usually weather or ATC...
-JMP