Since the 748 has somehow landed in this thread, let's not forget that the RAF's Andover version, with its fancy undercart, rear loading ramp an' all, could barely lift itself off the ground in hot conditions, even at sea-level, let alone a payload.
When the glorious Twin-pin was sacked from Sharjah, the Andover replacement sometimes picked up less for a particular sortie than the Twin-pin would have done in the same conditions. That was, admittedly, partly because the Andover flight's idea of a suitable diversion fuel load was a bit different from the Twin-pin flight's more pragmatic notions.
It also brought with it an intolerable amount of bureaucracy; we had to "check-in" 30 minutes before a flight instead of rolling up to the aircraft in a Landrover while the engines were starting, at SHJ at least, but that's another story. They wanted to take our personal weapons as well, but they lost that one.