Microwave Landing System...
The only airport in Australia fitted with the system was Canberra (CBR)
I beleive it was an Austaralian invention more acurate than other ILS systems
Was to be fitted to many comercial aircraft in Australia until GPS made it somewhat redundant.
Only aircraft I have seen with MLS systems were ex BA 767 operated by QF. Fitment was by BA for landing at LHR etc where landing in PEa soup is a common thing.
I have not heard of any new MLS installations at airports due to local GPS ground stations being fitted to many airports for accurate GPS approaches.
Only way MLS will get up again is if the USA threatens to turn off GPS systems
My 2 cents