An airplane waiting for takeoff on the runway

If you’re looking to take a late-summer break, you'll be happy to hear that Labor Day flights are expected to be the cheapest in four years, according to Hopper, a travel app that forecasts flight prices.

On average, domestic airfare prices around Labor Day weekend are expected to be around $255 this year. In 2015, domestic airfare for that weekend averaged $294, according to Hopper.

According to its Labor Day Air Travel Forecast, which Hopper released Wednesday, trips to the southeast from all other parts of the country will have some of the best bargains, with round-trip flights to Fort Lauderdale, Fla., Myrtle Beach, S.C., Orlando, and Atlanta averaging around $200.

More On Air Travel

The low-fare prediction for the Labor Day holiday follows a summer in which the average price for domestic and international airfare has also been the lowest in years, mainly due to the competition the major carriers are feeling from low-cost airlines.

Not even a significant increase in the price of fuel, which happened just before the busy summer travel season, did much to boost the price of an airplane ticket.

"Oil is getting expensive again, but no one wants to be the first to raise prices,” says Patrick Surrey, chief data scientist at Hopper.

Another reason prices have stayed low is that airlines, especially low-cost carriers, get more of their revenue from fees, which shield them from fuel price fluctuations, according to Jay Sorensen, president of IdeaWorksCompany, an aviation industry consultant. So when fuel prices rose, carriers could continue offering cheap airfare, Sorensen said.

Why You Have to Act Fast

But just as the summer inevitably fades to fall, the low-price environment is not expected to last forever.

“In the medium-term, especially if the price of oil stays high, we expect airlines to start raising prices again,” says Surrey, especially as the winter holiday travel season approaches. So, if you have a trip coming up this winter or spring, it’s smart to buy your tickets now.

“This may be the last hurrah for cheap airline tickets, so don’t put off buying airfare for a big trip,” Surrey says

You'll also have to act fast to snag the best Labor Day deals. Incremental price hikes will begin in the two weeks leading up to the holiday, says Hopper.

If you have some flexibility, Hopper says you may get an even cheaper price if you leave on Saturday, September 1 and return on Wednesday, September 5.

Don’t want to travel on a Saturday? You can also save by shifting your departure to earlier in the week, with big discounts for Aug. 28 and Aug. 29, Hopper says.

Avoid the Fees

But even the best airfare bargain in the world can be a bust if you don't take steps to minimize the fees airlines charge for ordinary conveniences like checking a bag or choosing a seat or boarding early. 

These fees can quickly make a price of a low-cost ticket approach that of a regular fare.

“They nickel-and-dime you for everything,” says Cynthia Marrs, a 76-year-old, from Junction City, Oregon, who recently flew on Allegiant Air.  “They gave me these dimensions for my carry-on, and I measured my little bag, making sure that it was OK. I was so careful.”

Still, she didn't realize the airline charged for carry-ons, so she got hit with a $34 fee.

While some fees can be tough to avoid, others can be sidestepped or minimized. Here are some tips:

Baggage fees. Register your intent to check a bag during the booking process to get a discount. For example, travelers who inform Allegiant Air of their plans to check a bag during the online booking process pay $22 per bag, vs. $45 if they check a bag at the airport. Norwegian Air, an international carrier that normally charges $100 per checked bag, offers baggage fee discounts of 50 percent to passengers who alert the airline of their plan to check bags at least 6 hours before departure. Other airlines offer similar discounts.

Seat selection. Before deciding to pay more for a “better” seat, do some research using Plug in the flight number and time of departure, and SeatGuru will show you the seat map of your plane and describe whether the seat reclines, how much legroom there is, whether a window is misaligned, and which seats are located near brighter and louder areas of the plane, such as the bathroom or kitchen galley.

WiFi access. Check to see whether your credit card gives you free WiFi access. For example, The US Bank FlexPerks Visa card offers 12 free Gogo internet passes each year. This card is available with no annual fee the first year and a $49 annual fee after that.  

In-flight entertainment. Download your own TV shows or movies. While many airlines offer free in-flight entertainment, their offerings are more limited than those of popular streaming services. So if there’s something you really want to watch on your journey, make sure to download it onto your tablet or laptop before you leave your house.