Before you go you have to check: Model, callsign, time and date(when it is valid), filed level (if you think you might get a lower level, you'll burn more fuel), reg, routing (just to make sure it's something you can expect, sometimes there are some new restrictions that prevent you from using the planned route, you end up burning more fuel), winds(if time and date's wrong, then your winds are wrong too), EZFW (check with your own calculated ZFW), ELW/ETOW (check that neither exceeds your max), flight time, add. items.. What it all comes down to, after checking the above, is what amount of fuel do you need/want? Bringing plog fuel might get you in trouble if you don't do your preflight properly. Just from the top of my head, I'm sure I've missed something...
It's a good idea to make sure that the plan is for the correct type of aircraft. I remember one hero getting airborne and then, some time later, noticing that where it should have said DC10 it said B707!
Or,as it happened to me ,going on a night stop flight with a fpl for a 737-700 and returning with a 737-300 one (just one wrong id letter)
I thought ..'strange', in the morning when the loadsheet ZFW was 'a bit' different than the fpl estimated one ,but when the f/o informed me that we are over the MLW the coin dropped...
we had'nt got enaugh time to check the return fpl ,before departing...so.
TopBunk: Yes, I am afraid you are correct. In Ryanair we never check the wx before we go...we just don't have enough time. Thunderstorms, RVR, turbulence who cares really? The show must go on. In fact we just show up at the gate...no checkin whatsoever.
The first computer flight plan I saw was one developed by R. Dixon Speas for the B707, circa 1974. Dead accurate*, even better than what PanAmerican was using at the time. So-called computer flight plans can lead you right and truly down the slipprey slope, IF you don't check 'em carefully.
*How accurate? Plus or minus two minutes on an Atlantic crossing. Dixon Speas had the old IBM computer system, and it worked like a charm, even if it did consume half the electric power in Buffalo, New York.