The Cletrac M2 was used to tow bombers and fighters (US Mustang squadrons each had three of them and the bomber squadrons probably had more) on the airfields in WW2 and being equipped with a winch, 110v generator, and 2500 psi air compressor, was used to service the aircraft too. I've attached a photo of my M2 pulling the B17 "Memphis Belle" from the movie at an airshow in 2003. Here's a link to a bunch of pictures I had posted on the Cletrac.org site.
http://cletrac.org/pages/model/pic-MG.html
They have a 150 hp engine and it's amazing how much power it has for a 1943 machine. I asked the B17 pilot why they needed that much power and he commented, "Sure the bombers are easy to pull like this but spang one into the runway when there's 50 more waiting to land and you need all the power and traction you can get to pull the wreckage out of the way for the next guy to land.
Cletrac made about 8300 of them but from what I can discover there's probably less than 50 complete restored machines left. That makes them quite rare. Mine is likely the only RCAF example in existence. It was used at a British Commonwealth Air Training Plan airbase at Prince Albert, Saskatchewan with a grass runway and lots of snow so the available traction would have been greatly appreciated.