The game itself is fairly simple. You own an airline and start off most missions with two decent airplanes. You have to build yourself up and defeat your competitors or meet certain objectives. The biggest aspect of the game comes in the form of the flights. You usually get orders from travel agencies to cater a specific flight for a fee. It is also possible to start running your own routes by leasing them from the manager.
Airline Tycoon mainly excels because of its diverse nature. Placing the orders on your schedule is simple and quick. It's just an exercise in knowing what your airplanes can do and scheduling the flight. You can go much further though. You can hire better pilots, hire advisors to get discounts and analysis, speculate on petroleum prices, take cargo orders, buy new airplanes, buy old airplanes and restore them, and even buy stock in the other airlines with the hope of buying them out soon. There are also little tricks and puzzles to solve. For example, you can go through a little side quest and get superglue that locks a rival in place for an hour. There's even a full sabotage option available for you to explore with the right side quest.
The game is also a fun and cartoony experience. Each of the rooms has little secrets and jokes. The characters are all over the usual range of stereotypes. The passengers are all “unique” in one way or another.
That's one of the other cool aspects. You conduct your business by moving through the airport or placing phone calls. Your orders are real and passengers will arrive to check and pick up their luggage. It gives the airport a “busy” feeling that I personally like.
The downside is that the game gets a bit repetitive. A lot of the extra features are also not integrated well. Upgrading your airplanes and managing your staff properly doesn't net you much of an appreciable reward. These are just minor nitpicks though.