some Soviet aircraft ( Tu-154 and IL-62) electric starters were not used to save weight, so a different method of starting the engines was required, a van with a jet engine to couple to the aircraft to inject 200 degree C hot compressed air to the jet engines.

This heated and compressed air is supplied through a flexible rubber sleeve 12 m long to the aircraft’s on-board fitting and heated up to 200 - 220 ° С for start-up. In addition, the van engine drives two generators that feed the aircraft's onboard systems.

http://carakoom.com/blog/uaz-pokazal-arhivnye-fotografii-buhanki-s-samoletnym-dvigatelem