Okay, if you're late to the airport, you might not be late to your flight. Maximize your chances of making your flight, even if you're late to the airport.
Step 1, knowledge:
- Most domestic flights require 30 minute before your flight takes off check-in time. SFO, JFK, and other major airports have upped this to 45 minutes. Play it safe. Check in on your phone in transit to the airport, even if you plan on using the kiosk to get a piece of paper for whatever reason.
- Gates close 15 minutes prior to departure for domestic flights.
Step 2, move quickly through the airport.
- Don't check a bag. If you check a bag, don't be late to the airport.
- Tell the people at the TSA line when your flight is and show them that you're late for it. They'll usually let you skip the line.
- Use the ticket on your phone that is scanned, don't bother with the kiosk ticket.
- Run.
You can usually rebook stand-by for free same day. Same day to airlines means "in the same calendar day in your time zone". It's useful here to also realize that you're allowed to rebook to airports in the same municipal area even if it's not the precise same airport. So, if they don't check for you, remind them to check for potential flights you can stand-by onto to all of EWR, JFK, LGA, even if your original flight was for LGA. I've used this tactic to rebook onto a flight to a preferred airport that actually got me to my destination faster.
If you're paranoid (if you're truly paranoid, why were you late to the airport?), you can get a confirmed same-day change for $50/$75 on the "old school" airlines, and something like $100 on Virgin America / JetBlue / whatever startup airline launches tomorrow. Usually I make the call of whether or not to get a confirmed ticket or stand-by by asking the agent who's rebooking me how many empty seats there are, and whether or not they think it's safe to fly stand-by. Just ask, they have better instincts than you on this regard.
This happens to everybody who flies too much, eventually. As soon as you find out that it's canceled, or, as soon as you find out that a delay could potentially cause you to miss your connection, get on the phone with your airline. Frequently this has shorter wait times for rebooking your flight than in person does. Don't take the gamble though, and immediately move to put yourself in the in-person re-booking queue, wherever that is at the airport you're at (sometimes it's at the gate that your flight was scheduled to depart from, sometimes a generic customer service desk is closer and less busy. Make that decision while on the phone with your airline, waiting to be helped)
Know how long each of the legs of your flight take, so that you can easily determine if a delay could cause you to miss your connection. If the delay would put you at the airport with < 20 minutes to make your connection, assume you'll miss it and go ahead and implement all the previous steps.
Final piece of advice is that airline software is super crappy, and whether or not you get rebooked onto a flight can sometimes depend on your agent's ability to use the interface. If you don't get the answer you like on the phone, hang up, call back, try another agent.