Originally Posted by
RAT 5
It should not happen en-route to destination. That would mean you had already used your diversion fuel, and therefore should already have diverted.
There is no legal requirement to divert when reaching alternate fuel + final reserve. You can always continue to destination, subject to commander's assessment of operational factors (traffic, ATC, weather, runway avaiability), as long as you ensure you land there with at least final reserve (30 minutes).
When you actually commit, and you
may/might land with less than final reserve, you should declare "minimum fuel". Nevertheless, when you are sure you
will land with less than final reserve at any suitable airport, you should declare "mayday".