A jetway is what is also called an air-jetty, air-bridge, jet-bridge and a few other words; a tunnel leading from an airport terminal gate to the door of a plane to assist boarding and disembarking.
The floors of these jetways often have bumps (nubs) on the floor which were engineered for safety ("safety-engineered") by making one less likely to slip if the floor gets wet.
Rolling suitcases, the type that one trundles along on wheels often make a droning sound, especially loud in a jetway due to the acoustics of such a tunnel. To say that they drone like jet planes is perhaps a piece of hyperbole, but still this just means that they make a very loud droning noise. So:
Over the safety-engineered nubs molded into the jetway floor, their rolling suitcases drone like fighter planes.
As you turn you may lean slightly to the side you are turning. Rolling suitcases are even more inclined to do so, lifting on one side.
This sort of motion is called banking and while we don't often use it of people or suitcases, we do regularly use it of planes, so the choice of word evokes the jet-fighter imagery of the previous sentence.
Considering that earlier sentence, "Randy is in Tokyo’s airport, ambling down a concourse with a slowness that is infuriating to his fellow travelers." the "they" of both these sentences are these fellow travellers.
Hence the same thing could be rewritten as:
Going over bumps moulded into the floor of the connecting tunnel between the terminal and the airplane, their rolling suitcases made a very loud droning sound. As these suitcases lean to one side as their owners turned around his large body, the suitcases grazed the backs of Randy's knees.
The original though does a better job of conveying a sense of place, both in its terseness and in the jet-fighter simile.