Planes and cars are different animals (I would hope this goes without saying).
Also, since the topic of cars has been introduced a Prius is rated to carry somewhere around an 840 lb payload, which is incredibly low, for comparison a Mini Cooper can do almost 1000. The whole idea of carrying engines around for the sake of "boosters" is just nonsensical, if there was a way to incorporate one as an APU it MIGHT be worth looking at. Even then, the additional costs associated with an idea like that in civil aviation a) don't make any financial sense, and b) have not made financial or operational sense in the past.