So as a reader one can assume that either a) I forgot about the wings (I guess I must be an idiot) or b) I am using a broader set of reference objects than simply "current passenger transportation modes". There are many man made objects much bigger than airplane wings. Fitting an aircraft carrier, or a container ship, or a skyscraper, moving under a city, would be much, much harder than fitting an airplane. Not to mention that if we strongly applied this engineering constraint, it's not beyond the realm of imagination that we could produce airliners with removable or foldable wings, or where the passenger compartment slides out, or tunnels with deep grooves for the wings, etc.