You wait at the gate desk when your flight is cancelled
Don't get discouraged over a cancelled flight just yet. The best way to handle an off-schedule flight is to call the airline as you wait on line at the ticket desk. There's a good chance you'll reach a phone agent first. Equally as important, you won't have to negotiate with the same frazzled agent who's dealt with dozens of similarly disgruntled fliers. These are the things airlines won't tell you (but every flier should know).
You expect non-peak crowds on peak days
Larger crowds lead to more chaotic parking and drop-off situations and longer wait times at security checkpoints. Plan accordingly. In general, airports are most crowded on Monday mornings and Friday afternoons, as these days bear the brunt of business travel. Expect Fridays to get even busier in the summer months as recreational travel peaks. You'll find the biggest crowds of the year on Thanksgiving Eve as well as the Sunday after it. And unsurprisingly, the busiest week to fly is the one that falls between Christmas Eve and New Year's Day; the Department of Transportation found that the number of long-distance travelers during this period rises by 23 percent. (These 4 letters on your boarding pass guarantee you'll have a longer wait at airport security.)
You accept the first voucher on an overbooked flight
If your flight is overbooked, don’t accept the first voucher that comes your way. Airlines typically increase their offer until there are enough volunteers willing to give up their seats. If the airline bumps you involuntarily, insist on cash compensation instead of a voucher. (Make sure you know your rights as a passenger if your flight is overbooked.)
You don't visit the airport lounge during a long layover
For infrequent flyers, it’s hard to justify the several-hundred dollar annual fees that are associated with airline lounges. But if you’ve got a long layover, it might be worth it purchase a daily pass. One-day passes are available for Admirals Club, Sky Club, and United Club, all for $60 or less. Amenities include everything from complimentary snacks and drinks to Wi-Fi and shower suites. (Here's how to make the most out of your airport layover.)
You don't check in to your flight ahead of time
Along with saving you valuable time at the airport, checking in to your flight ahead of time can earn you bonus miles and help you score a better seat. (Here's how you can use your credit card's rewards program to score the best vacation ever.)
You try to avoid motion sickness by upgrading to first class
While a last-minute upgrade might seem like a good idea—especially if you often find yourself falling ill on flights—the seats in the middle of the plane are best for those with motion sickness. "A plane is like a seesaw. If you're in the middle, you don't move as much," Patrick Smith, pilot and author of Cockpit Confidential told Reader's Digest as one of the secrets your airplane pilot won't tell you. More worried about safety than nausea? This is how to survive a plane crash.
You don't measure your carry-on
Because carry-on requirements vary by airline (9"x14"x22" is standard for Delta, United, and American Airlines; Southwest allows 10"x16"x24") it's best to confirm space allotments and measure your bag before you pack. And if you stuff it to capacity, measure the suitcase again before you leave. Avoid these common suitcase packing mistakes.
You never check airport monitors for flight information
While it's great to subscribe to flight-status updates on your smartphone (sign up for these when you check in to your flight), don't use them as your only source of information. Airport monitors are still your best bet for the most up-to-date information. Double check your gate before you get on the trolley that takes you to the other side of the facility. (By the way, here's a map with airport Wi-Fi passwords all over the world.)
You pack liquids deep inside your carry on
Make security checkpoints a breeze by packing liquids (which are all 3.4 ounces or smaller and zipped into a 1-quart Ziploc bag, of course!) into an outside pocket of your carry-on. Laptops and tablets fall into the same category. Check out the TSA's website for a full list of items on the no-fly list as well as tips for getting through security quickly.
You forget a pen on an overseas flight
You'll need a pen to fill out immigration forms on board. And your flight attendant will appreciate not having to supply the entire flight with extra ink. (This is the best airport in the world.)