Somewhat more important is the knowledge how to calculate extra fuel required. In many airlines there seemed to be weak education. I always asked the F/O first what fuel they wanted. Looking at the weather there was the comment that perhaps we needed a little extra and a figure or 300 or 500 or 700kgs was plucked out of the air. No calculation or realisation of what that would allow you to do. There was eye opening when I put some numbers down in a list which included 15 mins hold, 2 approaches, (might be circling) 5 mins to organise a diversion from a non-radar airfield and then divert to an alternate with an NPA and arrive feeling comfortable on fuel. The extra fuel this calculated was quite a bit more than 'a little extra'. The next question from the F/O was "are we allowed to do that?" Heaven help us.
There was also the intercontinental charter airline flying Europe to a Caribbean island with no radar and procedural NPA, who insisted that we carry FPL fuel because the contingency fuel was about 45mins and that was enough extra. I tried to point out that we were flying west, usually a head wind jet up to 150kts which we would try to avoid, but...... with an Atlantic CRZ of 7 hours into this headwind and perhaps optimum -2000'. The contingency would disappear. The Alternate was another similar island. The return crew was at destination and on minimum FTL's to make the return trip. The a/c had to land at destination even if it meant holding for 1 hour to allow the crew make the return flight within FTL's. etc. etc. We never left with less than comfortable sensible fuel. It would depend on the jet, strength & position relative to track, and destination weather. Sometimes it was minimum fuel, often not, but the lack of understanding & courage from the F/O was disturbing. It is very easy to brow-beat brain wash & clone pilots. Is that safe? Another issue in the maze of safety discussions.