Memorial Day weekend is upon us, kicking off the busy summer vacation season, and airlines are forecasting that this could be their busiest summer ever. Industry projections indicate that despite relatively high airfares, U.S. airlines could carry a record number of passengers this summer, even though they're still operating fewer flights than before the pandemic.

The coming months are likely to be a "stress test" for a national aviation system plagued by recent staffing shortages, antiquated technology, air traffic control problems, scheduling issues and labor disputes.

After widespread flight delays and cancellations last year, consumer advocates and some within the travel industry worry air travelers could face similar disruptions that will mess up their summer travel plans again.

If you're among those hoping to jet off to somewhere fun this summer, here's what you can expect.

Long lines and packed planes starting this weekend

"This summer's travel demand will be as strong as we've seen since before the pandemic and potentially the strongest ever," says Geoff Freeman, president and CEO of the U.S. Travel Association, which represents airlines, hotels and other travel-related businesses.

The crush of travelers starts Memorial Day weekend, with AAA forecasting that about 3.4 million Americans will be flying this Thursday through Monday.

Including the numbers of commercial airline flights and those on smaller general aviation aircraft, there will be more than 313,000 flights over the seven-day holiday period from May 24 to May 30, according to the Federal Aviation Administration. While that is just below pre-pandemic 2019 levels, the airlines may actually be flying more people by using bigger planes than they normally would on many routes.

The FAA projects that this Thursday will be the busiest day of the Memorial Day weekend, with more than 51,000 flights forecast.

Among the commercial airlines, United is predicting this Memorial Day weekend will be its busiest in more than a decade. Delta expects a whopping 17% increase in passengers from last year.

"The airports are packed," says Steve Solomon, chief commercial officer of the Airlines Reporting Corp., which processes and tracks airline ticket sales. "So travelers should prepare to get to the airport early, allow adequate time to get through security screening, through the TSA, and expect to see a lot of people on really full planes."

Solomon says Europe is especially popular this summer, with huge increases in the number of airline tickets purchased for the top ten destinations across the Atlantic, even though prices are up significantly.

"Summer 2022 was pretty rocky"

If last summer is any indication, air travelers might be in for some turbulence before they get off the ground this summer.

"Things were very bad for air travelers last year. They were as bad as they've been in 25 years or more," says Andre Delattre, national program director for PIRG, the Public Interest Research Group. The consumer advocacy group analyzed airline passenger complaints filed with the U.S. Department of Transportation.

"There were five times more complaints in 2022 compared to 2019 before the pandemic, even though fewer people were flying," he says.

Airlines delayed and canceled a staggering number of flights last year — more than 210,000 were canceled, according to the flight tracking firm FlightAware. "Other than the early months of the pandemic, that's more canceled flights than any year since 2001, when, of course, 9/11 disrupted air travel," Delattre says.

A recent Government Accountability Office investigation found that the sharp increase in airline flight disruptions in recent years was largely caused by factors within the airlines' control, including maintenance issues, technology glitches and staffing problems.

Even though taxpayers shelled out $50 billion to keep airlines in business and pilots, flight attendants and other employees on the payrolls during the pandemic, airlines offered early retirements and other incentives for workers, including experienced flight crews and ground crews, to leave.

Then air travel demand returned much more quickly than airlines expected. Many tried to cash in with aggressive scheduling, but the staff was stretched too thin to meet that demand, especially during severe weather, which led flight crews to time out without fresh crew members to replace them. With planes and flight crews out of place and too few replacements available, it would take some airlines a week or more to get caught up from one series of thunderstorms.

Add to that a new pilot training backlog, and shortages of mechanics, maintenance workers, gate agents and customer service staff, along with technology glitches and outdated scheduling software at some airlines, and it all cascaded into several periods over the last year in which hundreds of thousands of would be travelers were stranded, the worst of which was over the Christmas holiday, when Southwest alone had to cancel 17,000 flights.

Airlines say they're better prepared now

American and its rival airlines all say they're much better prepared for this summer than last. They've all gone on a hiring spree, with passenger airlines adding nearly 4,500 employees just in March alone.

The industry now employs more than 486,000 workers in the U.S., nearly 10% more than they had before the pandemic.

Most airlines handled the recent surge in spring break travelers relatively well, and the cancellation rate so far this year is down significantly from last year. According to the federal Bureau of Transportation Statistics, airlines canceled 1.7% of flights over the first three months of this year, far lower than the 2.7% flight cancellation rate for all of last year, and 4.1% for the first quarter of 2022.

"We are as prepared as we can possibly be," says Nick Calio, president and CEO of Airlines for America, the lobbying group representing the nation's biggest air carriers. "We've got a lot more employees. We have reduced our schedules and adjusted how we're flying," in an effort to minimize flight disruptions.

But many industry experts warn travelers to be prepared for significant flight delays and cancellations anyway, caused by things outside of the airlines' control.

The FAA's air traffic control issues

While the Biden administration is turning up the heat on the airlines to fulfill their obligations to passengers, the airlines are growing frustrated with the federal government's own aviation shortcomings.

The FAA warns that a significant shortage of air traffic controllers overseeing the very congested New York area airspace could increase flight delays into and out of Newark, LaGuardia and JFK airports by 45% this summer.

In addition, the chronically underfunded FAA is also struggling to replace outdated technology. The failure of a pilot notification system in January led the FAA to briefly halt all flight departures nationwide, causing thousands of flight delays and cancellations that day.

Meanwhile, Customs and Border Protection staffing shortages in many airports has led to hourslong waits for international travelers returning to the U.S. to get through customs.

Geoff Freeman of U.S. Travel puts the blame for many of these problems not on the airlines, but on Congress and the federal government.

"These problems have come out of years and years of underinvestment," Freeman says. "If the government doesn't act now, the headaches won't just happen during peak travel season and holidays, it will become our daily reality."

Summer air travel tips

Airline passengers who run into problems from flight disruptions to lost luggage this summer can find out more about their rights and the airlines' responsibilities at the Department of Transportation's Office of Aviation Consumer Protection. The site also links to a dashboard listing which airlines are willing to pay for meals, ground transportation, hotels and other expenses incurred because of significant delays and cancellations that are the airline's fault. It also link to a site where consumers can file complaints.

Experts recommend booking flights earlier in the day as storms tend to develop later in the afternoon and evening. It's also a good idea to check the weather forecast for your destination and any cities where you have a layover. The FAA has a site showing where severe weather may cause problems for air travelers each day.

Use the airline's app to track not just whether your flight is on time, but where the plane is coming from and if there are delays there. Book nonstop flights, if possible, so you don't get stranded on a layover.

Travelers who are checking luggage should also be sure to pack an extra change of clothes or two and medications and other necessities in their carry-on bag, in case there's a significant delay or cancellation after you've checked in.

The bottom line for those of us flying this summer is to plan ahead, prepare for the worst — and hope for the best.