I recently came across Itasoftware.com as a place to check flight schedules. I know a number of the mileage runners find it invaluable. I have found though, that for itneraries I am looking at within Asia it seems to be incomplete. For example I searched for flights from PEK to SIN. While SQ has non stop service on the day I was looking ITA only shows connecting service through HKG using Air China. I have found simlar situations so many times that I am thinking that ITA is not a useful resource.

Any of you who use it regularly have any further insight?