In the 1970’s, when everybody and their brother was thinking of ways of dealing with oil shortages and the like, Boeing studied the idea of using giant aircraft to carry oil and/or natural gas from Alaskas north slope down to the lower 48. Quite a number of these aircraft were designed; the math seemed to work on the aircraft being possible, but the math didn’t seem to work on them making economic sense. One of these crashes… hoo boy. Still, the idea of watching the Keystone pipeline protestors heads asploding when seeing these monster planes fly over would almost make the risk worthwhile.
Shown below is a photo of a model of one such design, capable of hauling a two-million pound payload (about 10 times the 747’s capability).
One of these decades I’ll probably do an APR article on the concept.