From the best of my knowledge, SQ
has sort of stopped getting anymore work experience students due to 'limited personnel in taking care all work experience students thoughout the year, unless you know someone from administration or management.' (At least, that's what I have been told by a few Australia-based SQ
employees, including one of regional managers)
With Qantas, depending on the time you contacted them, in most cases, you have to contact them at least 12 months in advance (esp with customer services and similar kind), but fewer months would sometimes also be considered for certain positions speifically allocated to 'work experience students'.
In fact, many of smaller regional carriers take a lot of work experience students and I personally know National Jet System does have quite a few vacants available for work experience students across the country. By the way, some international carriers DONOT take work experience students at all and I suggest you to lodge your CV
or Resume face-in-face whenever you could, because most phone calls & emails would simply get a reply of 'We have no work experience program this year, but we thank you for interested in XXXXX,' when they actually do have programs for work experience students.
Hope this helps in one-way or another.