Here is one free startup idea for you. Groupon/Airbnb/Ubercab/whatever for airlines tickets. Not another cheap ticket search engine plz. If somebody will do it I will be lifetime customer (i even ready to become investor if you need some money and have right team)
Airlines tickets sales is one of the biggest e-commerce businesses. I know its very tou to disrupt spaces but i am 100% sure that someone who will be able to do this will be huge winner.
I am frequent flyer and fly between Europe and US/within US few times/month. My schedule is almost always flexible and I am always looking for cheap tickets. There are almost always free seats in plane. I am sure airlines will be interested is some SMART way of selling them for discounted prices.
Most of startups are just search engines for ticket prices. What I am suggesting might be more like demand data analysis => discounted offerings generation thing. Another way might be doing something like crowdsourcing charter jet flights. Anyways I am sure this space still waiting to be disrupted.