Windsor said
Any time our FOB is less than planned at a specific waypoint or if our EFOA goes below our planned FOA, it requires an acars to dispatch letting them know whats going on. If you catch it early, a min fuel situation can most likely be avoided. ATC delays ect....are a whole new ballgame and will be dealt with slightly different.
How far off the planned burn do you have to be to generate a message to dispatch?
And yes, P5 (prior planning prevents p*ss poor performance).
Here is another situation that is coming up in the ASRs. Dispatch gives you an alternate and crews have sometimes found they do not have the approach charts for that airport OR there is a notam which precludes an approach.
Also, in some cases, the nearby alternate is being used by everyone else and that airport gets slammed with arrivals it can't handle.
So, yes, the earlier one begins to search options, the better.