that kind of technology is attributed to a plasma drill, the idea is there is a strong hot plasma made infront of something that melts the rock and thermal design so that the rock is solidified after the craft to form a tunnel.
https://en.wikipedia.org/wiki/Plasma_deep_drilling_technologyI would say it more like.. swims through rock rather then flies. If you superheated everything to make a gas bubble you could fly like cavitation craft, but that is technology... 10m years in the future maybe lol
If you want it fast you would need some kind of chiller to solidify the rock fast enough so there is not a bunch of lava behind the craft (different thermal conductivity and specific heat of lava), also possibly some kind of thermionic cooling effect would need to be used for that
But IMO not that crazy, its kind of like cutting through ice with a string, Just very hard.
Often done with plasma cutters to put holes in metal, but its not that good because usually the hole is hardened as fuck (nitrided), so its hardly a good pilot hole, I would prefer virgin steel (but it could serve as a OK pilot hole for an annular cutter center shaft if you got that)... if you deal with plasma cutter you know how much of a bitch hardened steel on the edge can be, thats what they hide in the brochures about productivity, it seems much worse then oxyfuel cut steel. Best way is to smack it with a hammer and chisel if you don't mind deformation to crack it of, then grind.
A combination approach is interesting too, if you have the power, to crush the rock with carbide cutters then melt it on the back 'exhaust chute' to make a glassy tunnel