(NewsNation) — Airlines that have stumbled badly over the last two holidays face their biggest test yet of whether they can handle big crowds when July Fourth travelers mob the nation’s airports this weekend.

Problems popped up well before the weekend, with some disruptions caused by thunderstorms that slowed air traffic. AAA said Friday is the busiest day to fly this weekend.

Travel experts are warning, if you’re getting on a plane, have your Plans A, B and C ready to go. Another good rule of thumb is to download the airline’s app on your cellphone and you can work on rescheduling any potentially canceled flights right from your phone.

American Airlines canceled 8% of its flights on Tuesday and Wednesday, and United Airlines scrubbed 4% of its schedule on both days, according to FlightAware.

“It’s a high-stress time for everyone, pilots, flight attendants,” Clint Henderson, managing editor of news at travel website The Points Guy, said.

Holiday revelers who are planning to drive face their own set of challenges, most notably high gasoline prices. The nationwide average has eased since hitting a record $5.02 in mid-June to $4.84 a gallon on Friday, according to AAA, which expects prices to continue to ease because of rising gasoline inventories.

Americans are driving a bit less. Gas demand last week was down about 3% from the same week last June, according to government figures. In a Quinnipiac University poll in June, 40% of those surveyed said gas prices have caused them to change their summer vacation plans.

Air travel in the U.S. is almost back to pre-pandemic levels. Since last Saturday, an average of nearly 2.3 million people a day have gone through airport checkpoints — down just 8% from the same days in 2019. If that trend continues through the weekend, records will be set for flying in the pandemic era.

Airlines may not have enough planes and flights to carry all of them, especially if there are cancelations due to weather, crew shortages or any other reason.

Airlines have been caught short-staffed as they try to hire thousands of workers, including pilots, to replace those they encouraged to quit when the pandemic caused air travel to plummet.

Many of the airlines, including Delta, Southwest and JetBlue, have trimmed summer schedules to reduce stress on their operations. They are using larger planes on average to carry more passengers with the same number of pilots. Those steps haven’t been enough so far this summer.

Delta Air Lines took the unusual step this week of warning travelers that there could be problems over the holiday weekend.

Starting Friday, Delta said they’re canceling 100 daily departures through August. Similarly, passengers flying with Delta out of Gerald R. Ford International Airport in Grand Rapids, Michigan, say they were offered  $10,000 on a Visa gift card or right into the wallets of passengers who had Apple Pay to switch flights.

The Atlanta-based airline said it expects the biggest crowds since 2019, and this will create “some operational challenges.” It is allowing passengers booked on flights between Friday and the Monday holiday to change their schedule at no cost, even if the new flight comes with a higher fare.

The Points Guy’s Henderson suggested flying out of a smaller airport if possible.

“There’s not as many people, there’s not as many flights, so you don’t tend to get bogged down as much,” he said.

Meanwhile, airlines are increasingly trying to blame delays on understaffing at the Federal Aviation Administration, which manages the nation’s airspace and hires air traffic controllers.

The FAA said it’s ready to handle whatever Mother Nature throws at it to keep planes in the sky and running on time.

“We have detailed plans to reduce weather delays as much as possible, but we don’t do this alone,” said Billy Nolen, the acting FAA administrator. “We work with the airlines to plan for and work around expected bad weather or any other disruptions. Every few hours there’s a teleconference with airlines and air traffic facilities to adjust plans if necessary.”

The FAA has a major facility in Jacksonville, Florida, that handles many flights up and down the East Coast. After a meeting with airline representatives in May, the FAA promised to increase staffing at the center.