Yesterday, one of the other students was out on a xcountry. He refuellued at the furthest out point, and proceeded to start the return legs of the journey.
However, on getting to the end of the first return leg, about an hours flying... he discovered that the plane had used way more fuel than expected... About 15-20 gallons was gone, when only seven or so should have been used.
It tuned out, that the fuellers in Waco, hadn't got one of the tank caps on correctly and that this allowed the fuel to be sucked out of the tank in flight, and of course, the student had watched them brim the tanks and put on the caps, and had neglected to stick and recheck...
CHECK EVERYTHING !!