Expats in any industry in Singapore are used to manage supply and demand for workers. Need more widget makers due to an increase in orders, hire some expats if not enough locals applying. Not enough work anymore, lay off the expats as they are dearer.
Anyone wanting a long term career at SIA would have been well advised to join on local terms which would have given better job security in return for a lesser package. A 55 year old ex BA Captain with a pension could afford the risk of an expat contract as he'd probably only be looking at one renewal and it wouldn't be the end of the world if he didn't get it.