any 'extra' fuel taken on in anticipation of the 20 minute holding at destination can easily be used up if you do not get the optimum levels or the winds are incorrectly forecast or you have to do a lot of unexpected vectoring around weather that wasn't forecast.
- so, you are saying, that in your experience, it is not unusual to eat
all your contingency and start to use up the planned holding fuel? Time to take a little more, I feel, or maybe get Ops to review the airframe fuel burns? I know what I would do. Incidentally, the 'short-haul/long-haul' bit is irrelevant - 5% is 5%, and it is
very easy to use
all your 150kg contingency on a 1 hour flight just by being held for take-off a few minutes, even without 'wrong levels', 'winds' or 'weather' - and you STILL need 20 minutes holding.
Anyway, as I said, whether they knew 1 hour, 2 hours or 5 hours before, they took a 'punt' at it and got it wrong - I'm sure they would agree? To end any flight on a Mayday due to insufficient fuel is not ideal.