I hope the Americans don't use this as an excuse to stick with their old school system. I guess in one way they are closer to the Kingdom of England than us Canadians are.
It's convenient to use feet because planes are stacked in 500' increments and not 152.4m increments. VFR (visual flight rules) flights are usually on the 500's (eg. 3500', 4500', etc. depending on heading) whereas IFR (instrument flight rules) flights are on the 000's (4000', 5000', etc.).
Knots are convenient because 1 knot is equal to 1 minute of 1 degree of arc on a great circle. If you're flying anywhere far away this ends up being important as a great circle is the shortest route between any two places.
Oddly enough, the metric system is useful with temperature because the standard lapse rate is 2 degrees per 1000' of altitude. So if you had to climb from 6000' to 8000' on an IFR flight plan, you would usually drop 4 degrees centigrade, which might be significant if it was raining out and it dropped below freezing. Having water on your wings and climbing up to an altitude where it's freezing is going to make you have a really bad day.
Wouldn't it be faster to adjust the heading to point directly to the destination and then fly in a straight line?
"In this case, the weight of a litre (known as "specific gravity") was 0.803 kg. (...) Between the ground crew and pilots, they arrived at an incorrect conversion factor of 1.77, the weight of a litre of fuel in pounds."
See, here's where metric system sanity checks become relevant, that are simply not possible with imperial because nothing is compatible with each other.
In metric, I just know, without any conversion factors to memorize, that 1kg water equals 1l at room temperature. Everyone with high school education should also know that gasoline products are lighter. Now I can do a sanity check - since the weight of one liter should be less than 1kg, there's no way 1.77 is right. If two well educated people do this math, at least one of them should see the mistake.