In the aviation industry, Memorial Day is often seen as the unofficial start of summer travel. That’s great news for airlines, which are expected to see their highest passenger totals in months.

This holiday weekend, approximately 2 million passengers are expected to pass through security checkpoints daily nationwide, the highest number of passengers since the start of the pandemic.

RELATED: New Economy Parking Lot Adds Option for Travelers

Recent data from industry group Airlines for America indicates the average load factor for flights operated by U.S. carriers was 83 percent as of May 27—up several points from early May. It is also the first time the average load factor has crossed the 80 percent threshold since the start of the pandemic.

“We’ve been very, very pleased with the pace of demand recovery,” Delta President Glen Hauenstein said at a recent industry conference. “Bookings have been better than expected.”

Passenger numbers continue to increase as volumes are currently running at 29 percent below average pre-pandemic levels, compared to 40 percent a few weeks ago. Airlines for America reports the number of domestic flights is down 25 percent. International flights, meanwhile, are down 50 percent.

Consumer trends and airline booking data indicate that leisure travel will make up most of the traffic for airlines this summer, while corporate travel is expected to remain sluggish until at least the second half of this year.

As a result, airlines have adjusted their networks to largely focus on leisure travel, said Dallas-based aviation consultant Rhett Morgan.

“The nice thing about airlines is that they are able to reallocate their assets,” he said. “It is not like a hotel you put on the corner and when demand changes, the hotel could be in trouble. The airlines are able to move planes around to capture that demand, which is really beneficial.”

Airlines benefiting the most from the shift in demand are ultra-low cost carriers, such as Allegiant and Spirit, that normally cater to leisure travelers by offering low fares to popular vacation spots.

In fact, Allegiant and Spirit, along with Frontier, are among the first airlines to fully recover from the pandemic. All three carriers plan to offer more capacity this summer than they did during the same period in 2019.

“Ultra-low cost carriers are the quickest to recover because, traditionally, they rely heavily on the leisure segment. They carry little to no business travelers, so they were impacted to a much lesser degree than legacy carriers,” Morgan said. “As a result, with demand returning, they are well-positioned in many of these leisure destinations.”

New flights at PIT

During the week leading up to Memorial Day, Pittsburgh International Airport saw the launch of several new leisure flights in time for the busy summer season.

On Thursday and Friday, United begins four new routes from Pittsburgh to Charleston and Hilton Head, S.C.; Pensacola, Fla.; and Portland, Maine. United’s new flights are all operated with its new Bombardier CRJ-550 aircraft—the world’s first 50-seat regional jet to feature a first-class cabin.

Meanwhile, Southwest begins nonstop service to Myrtle Beach, S.C. on Saturday, joining Allegiant and Spirit on that route. The addition of MYR comes after Southwest began nonstop flights to Sarasota, Fla., in March.

Other airlines have also made service additions from Pittsburgh that will begin over the next few weeks.

Allegiant continues to expand its network at PIT with flights to Key West, Fla., and Norfolk, Va., launching on June 3. They follow the resumption of Destin-Fort Walton Beach, Fla., on Saturday. In addition, the airline will begin flights to Rapid City, S.D., and Phoenix-Mesa, Ariz., in August.

Furthermore, American will begin seasonal service to Orlando, Fla., from Pittsburgh on June 5. Flights will operate on Saturdays through Sept. 4 on Embraer 175 regional jets.

Additionally, Southwest and Spirit will resume nonstop service to Cancun, Mexico, this summer. Southwest restarts weekend-only service on June 12, while Spirit returns with thrice-weekly service beginning July 1.

Recently, low-cost startup Breeze Airways announced PIT as one of the first cities it will serve. Created by former JetBlue founder David Neeleman, Breeze will add flights in July to Charleston and Norfolk, as well as new service to Hartford, Conn., and Providence, R.I.