This is really cool! Out of curiosity, where do you get the data right now? I've worked on a couple of projects, but always had trouble finding data for low-cost airlines other than just by scraping.

Also, just a few UI things that bugged me:

1. It would be amazing to show the price for each flight, in addition to the combined price.

2. I originally tried London Gatwick, but didn't get good results until I tried London Stansted. It would be great to consolidate cities' multiple airports into one.

3. When linked to the resulting sites, the site opens with the flight origin's country's language (e.g., a flight from Budapest would be in Hungarian), which makes it pretty hard to book. Can you link to everything in EUR and in English, especially if the site's English?

Overall, a great start! I'd totally use this if I just had a week free and were starting out in Europe.