shuttle has been in operation for about 30 years and until recently gave an excellent high-frequency, low-cost service between the two cities. However, in light of SARS - things have changed for the worse.
and MAS have reduced their flight frequencies on the route such that the so-called 'shuttle' service is almost now defunct.
In a nutshell,
1. You can book a reserved seat on any service with SQ
or MAS as you would normally book any other flight from anywhere in the world - MAS and SQ
offer First (F) and Economy (Y) fares on the KL
2. You can also buy a 'shuttle' ('YU
' class) ticket (which is what you are referring to) only by turning up at Changi or KLIA and paying up front (at the ticketing desks) and obtaining a 'queue number' - which will be called in turn, to fill any empty seats shortly before flights close. MAS and SQ
share this unique 'shuttle service' (probably the only one of its kind in the world) - as you can travel on either airline regardless - if you hold a 'Shuttle' (or 'U' class ticket) - ie. first-come-first-served-take-the-next-available-seat.
3. The above system worked brilliantly in the days when both carriers operated up to at least an hourly service - much like a bus-service and during the holidays - many flights were flown using 747s - full to the brim.
4. It was even better for some when the Malaysian Ringgit devalued as 'Shuttle' tickets can only be bought one-way and the fares were fixed, so it was much cheaper to buy two one-way shuttles and take advantage of the lower ringgit at the KL
-end - this however, was ok since there was rarely a problem with obtaining seats as a 'shuttle' holder.
I often have to do what you are doing at Singapore due to the lack of availability to KL
and decided that the best option is to arrive at Changi and proceed up to MAS' ticketing counter at check-in and ask how the shuttle loads are doing that day/evening or whenever. The staff would often give you some indication if loads are heavy or light and if its ok - save a few $$$ and pick up a shuttle number.
On the way back however (in light of the reduced services nowadays) - if it's a connecting flight you want and you don't want to risk spending the whole day at KLIA or Changi waiting or even risk not getting on a flight that day (almost unheard of!) - then purchase a normal 'Y' ticket to connect for your flight to the USA. You can certainly book and pay for this sector in Australia or anywhere indeed. Remember this KUL
fare will be in MYR - so will be cheaper anyway than a 'normal' SIN
Hope that helps - have a great time!
- If time is not a factor and you don't have much luggage - nip across to Johor Bahru and catch the JB
-KL service and for less than an Economy fare on the Shuttle - you get to fly in Golden Club!