system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do flights between states in the US typically cost in the hundreds of dollars while you can get flights between countries in Europe for less that $100?

I know the cheap flights in Europe are on crappier planes, I've flown EasyJet, but why is there no US equivalent?
gpt
* Air travel regulations

When you fly in the US, you have a choice of a few airlines.  You can select the major ones (American, United, Delta, Continental, US Air), the mid-range specialized ones with limited destinations (Alaska Air, Hawaiian Airlines), or the budget ones (Southwest, Jet Blue).  What do these have in common?  They are ALL US based airlines.  In Europe, they have an open-air policy in which airlines from other countries can fly you to places outside of their country.  This means more routes, more competition, and lower fares.   Foreign-based airlines can't fly domestic routes in the US.  In Europe, they can.  This means more distance for less money and competition means more options to popular cities.

* Laws

Another factor for US airlines are the laws which put a heavy burden on the airline industry.  Current laws limit foreign based ownership and how current airlines operate in the world.  For many US airlines, this limits their ability to compete in the global airline industry.  This means higher costs for US airlines, lower employment, and higher fares for consumers.  European airlines have more freedom to compete and can keep their costs lower for operations.

* Europe has a wonderful train system. Airline companies have to lower their prices to keep up. US has no such thing (Amtrak kind of sucks)