I do believe it is either 34 or 35. I know for a fact they have hired two people in their 30's (30, 31) in the last two years.
From what I understand they do like some people who are younger, and are less seasoned in terms of airline experiece because they do not like people bringing their previous company's attitudes with them. They are also looking for people who will be easily able to adapt to life in HK, in fact the entire interview process is geared towards finding out your devotion to living in China. This of coarse is for SO recruitment. FO recruitment is a whole different story. Average age bracket of SO new hires is usually between 26 and 32.
Cheers