My mention of Travel Agency was in reply to the OPs question. Of course you should use multipe travel sites to find times and fares, but in my experience, it seems cheaper, and safer, to go directly to the airline once you have found what you want. Let's face it, all sites SHOULD give the same schedules, and seats available.
If you do get into any difficulties, the Travel Sites do not have anyone at the airport to help, the Airlines do!