I think they're designing for their (original at least) intended audience, bargain shoppers. In which case, leaving that unchecked makes more sense, as non-stop flights are usually more expensive.

@Shawn - you may be right but the fact that it is on there just seem less than useful. I mean, if you check it and there are non-stop available, it clearly shows that in the results. I find it funny whenever I use the site that I need to check it.

As an (ex) programmer who has moved into the sales and marketing field, one possible reason is that the programmers did it on instructions from the top. It's possible that the Orbitz makes more money from flights with multiple stops. Since many inexperienced travelers/users may not notice that checkbox ...

@Calvin - you could indeed by correct, not sure how Orbitz makes money but more stops may be more money.

giving demand, non-stop/direct flights will usually be more expensive than multiple-stop trips. that said, perhaps by leaving the box unchecked the "find flights" search function will return more flight options, thus a greater chance the visitor finds one that fits into his price range and schedule.

i also know some people (my mom!) who prefer multiple stops to break up extended flights greater than 3 hours, but i reckon she's in the minority of those who flat-out fear flying.

Many inexperienced travelers/users may not notice that checkbox