Fly standby on American Airlines to have the chance of taking an earlier flight than the one for which you're scheduled. American allows passengers who have purchased full-fare economy tickets, passengers traveling on award tickets, frequent flier elites and premium cabin passengers to stand by for flights. It's also possible to stand by for the first-class upgrade list if you're an elite traveler on a confirmed economy class ticket.
Call American reservations at 800-433-7300 if you aren't sure whether you are eligible to stand by on the class of fare you purchased, at least a day in advance if possible. Travel to the airport as early in the morning as possible on the day of departure.
Present the check-in agent with your identification and a printout of your itinerary (if you have one). Inform her that you would like to travel on an earlier flight. If possible, the agent will offer you options for getting a confirmed seat on an earlier flight, although this may incur an additional charge. If not, the gate agent informs you of all the flights on which you may stand by, with the soonest one first.
Take the standby boarding pass the gate agent hands you and proceed to the gate for the soonest flight. Keep an eye on the monitors in the boarding area to see where you are on the standby list. Listen for your name -- when your boarding pass is available, the gate agent calls you up to the desk.
Go to the gate for the next available flight if you don't see a seat on the first one. Once the first flight fills, American automatically transfers your name to the standby list for the next available flight.
If you are a traveling on a confirmed economy ticket and are an AAdvantage frequent flier member, you may be eligible to purchase a place on the standby list using AAdvantage miles. Ask the check-in agent to see options for your specific flight.