Planes are booked full. So the next available flight could be hours or even days away. And if you’re stuck overnight, the hotel is often on your own dime.

Bumping happens because most big airlines regularly oversell their flights to account for no-shows — usually about one in ten passengers. It’s often prevalent around the busy Christmas or Thanksgiving holidays. But more travelers could be denied boarding this summer than a year ago because traffic is up while the airlines are limiting the number of available seats.

The Fourth of July weekend could be especially bad because of the number of travelers taking to the skies, says Anne Banas, executive editor of smartertravel.com.

If you involuntarily lose your seat, the airline has to give you cash or a voucher for $400 or $800 depending on how long you’re delayed from flying. The amounts rise to $650 to $1,300 staring in August.

But even the new amounts may not be enough to make up for vacation days lost, especially if you’ve booked a cruise or a nonrefundable hotel room.

Here are some tips for staying on your original flight:

— No seat? No go.

If the booking site doesn’t let you select a seat on your chosen flight, don’t book it. The flight is probably oversold.

— Check in early and beware the "seat request."

Gate agents often rank passengers based on their check-in times, so be sure to check in a full day ahead online. Those without a seat assignment will see the words "seat request." If this happens, check in with an agent at the gate once you get to the airport. Seeing your face before other passengers will help you avoid getting pushed off the flight.

— Know your airline.

Airlines vary widely in how many passengers they bump. You have the best shot at staying on the plane with JetBlue, Hawaiian and Delta. JetBlue doesn’t oversell its flights. It bumped just 26 of 6 million passengers in the first three months of the year. Regional carriers contracted by bigger airlines bump the most passengers. American Eagle, the regional carrier for American, was tops from January to March. It bumped about 3 percent, or about 6,200 of 3.6 million passengers.

— Be an early bird and fly direct.

Travel as early in the day as possible to avoid getting bumped by passengers who got bumped or cancelled earlier in the day. And select nonstop flights whenever possible. The more legs a flight has, the greater the chance you’ll run into trouble.

— Listen up.

Be ready to board immediately when your row or group is called. A gate agent could give your seat to a standby passenger while you’re hanging back.

Another way to avoid bumping, if you can afford it, is to pay for an upgrade to premium economy, business or first class. Coach passengers get bumped first. Building up loyalty points by joining an airline’s frequent flier program will also help.

Summer travel also means more cancellations because of thunderstorms. That could also mean a long wait for another flight.

There are ways to prepare for a cancellation. Airlines are required to display on-time performance on their websites. That includes the percentage of cancellations, if a flight gets scrapped more than 5 percent of the time.

Print out a copy of the airline’s contract of carriage, available on its website. That spells out what you’re entitled to if your flight is cancelled.

The airline’s customer service number comes in handy as well. You can call it while also waiting in the customer service line, a double-teaming strategy that gets quicker results. And jot down information for other flights leaving around the time you’re scheduled to depart. That’s ammunition for rescheduling your flight.

Even with that preparation, there’s a chance you’ll be stuck overnight — often without your checked bag. So, keep a change of clothes in your carryon. That’s also the place to keep your toothbrush and any medications you need.