coach domestic, $10 each way, plus $2.50 security fee for each leg (so if you are going houston-lax it is $12.50 but if you are going dal-iah-lax it is $15)
first class domestic, $40 plus above mentioned security fee(s).
international depends on where you are going. they have zones.
basically USA to mexico/south america/canada/hawaii/alaska is $30 for coach, $60 first class, one way.
usa to pretty much anywhere else (europe/asia), $50 for coach, $130 for first class, one way.
but also after your first year you get some vacations passes and they get you on the flight for free, and in first class if it is available. and at a higher priority. great if you travel internationally.