1) Just after 911 commissions for travel agents on domestic airfares where removed.
What does that mean?
You can get the same prices that travel agents do for US domestic airfare by going to the airlines website or other websites like Travelocity.com.
2) purchasing on line is cheaper than calling the airline directly over the phone
3) do a flexible date search even if you dates are fixed.
4) consider departing or arriving during the middle of the week instead of the weekend
5) some sites quote the price before tax. Others quote the price with tax. Always check to make sure what the final price with tax will be regardless
6) check the airlines website for additional fees for baggage, food purchase or other service items