In most cases, I doubt it.
Friends talk about all sorts of bargains they found on-line.
They also cite startling discrepancies from Web site to site. The search took 2 hours 17 minutes. It embraced 12 Web sites that profess to offer lowest fares. When I searched for flights by schedule, I got a few United and America West flights in addition at similar fares. In a sort of written guerrilla warfare, Web sites have sprung up to collect and voice complaints from the public about airline service and sometimes to wage personal vendettas by the webmasters in revenge for perceived abuses.