You're right. Lots of research and testing would need to be done. This is just a seed. I did think about a lot of this stuff, though. For one-way flights, you

You're right. Lots of research and testing would need to be done. This is just a seed. I did think about a lot of this stuff, though. For one-way flights, you just put one date in, rather than a range. As you pointed out, this has some problems. I'm willing to live with them for this mockup, though. For multi-stop flights, you click the plus button next to the destination. Users who are not looking for multi-stop flights would not be looking for a way to add a destination, but the plus sign is just forward enough that if you are, you would press it and find your answer. For the more advanced filtering stuff, I think it would be best to add those controls to the flights listing on the next page rather than clutter up the front page and first impression a user gets. Simplicity with progressive disclosure.