There used to be (and may still be) a guy named Hardy Prentice who
flat-towed his race-prepped Triumph TR-3 to Sports Car Club of America
races -- even from California to Georgia when the National
Championships were held there, as recently as 1992. (He towed it
behind an E-Type Jaguar; how's that for eccentricity tinged with
masochism?) There was no way that car was street-legal as a
self-propelled vehicle, but as a "trailer" all it needed was a trailer
license, an approved tow-bar and wiring from the Jag's taillights to
the TR's.

The only possible snags I can see in doing that with an airplane are
that an airplane's non-DOT tires may not be legal trailer tires in some
states and that some of the heavier airplanes, in some states, may
require brakes as "trailers". A solution to both problems would be a
DOT-tired, brake-equipped dolly with a long enough tongue -- shouldn't
cost an arm and a leg to cobble together.