Don't know it but as it should date from the pre-digital area, probably custom. /S reminds me a lot of Sepentine and I guess starting from Serpentine Sans might even quicker to reproduce it.

LECO1988-Regular (Regular *Oblique) from CarnokyType could easily be made into this older logo (available from MYFonts)

Qantas' ‘flying kangaroo’ retro-livery on its latest Boeing 737 to fly later this month

http://www.ausbt.com.au/qantas-to-unveil-retro-livery-on-boeing-737
Note the differences from the 1968 wordmark, here shown on a promotional ashtray

New version seems to have less slope. Different length of tail on _Q_ may be due to horizontal stretching?
Don

Posted wrong image - see edited version above.

The extra width of the retro livery lettering compared to the 1968 wordmark may be due, at least in part, to the result of the letters being on a surface that curves away from the viewer.
Don