Carriers have trimmed flight schedules, beefed up staffing, and invested in airport infrastructure and technology to be ready for the busiest travel season of the year, starting with the traditional kickoff on the Memorial Day holiday weekend.

Summer tends to be the most profitable season for airlines, but it is also the busiest time of the year, raising the stakes.

The Transportation Security Administration said Friday it screened 2.658 million passengers on Thursday, the highest number in a single day since November 2019.

Industry group Airlines for America estimates a record 256.8 million passengers will fly in the June-August quarter, up 1% over the 254.6 million passengers in the same period in 2019.

"It is kind of our Super Bowl," United Airlines (UAL.O) Chief Operating Officer Toby Enqvist told Reuters.

No one wants a repeat of last December, when an operational meltdown at Southwest Airlines (LUV.N) resulted in almost 17,000 flight cancellations, disrupting travel plans for 2 million customers.

The desire to travel for many is high, however.

Jihane Jeanty, 36, has planned trips to Florida, Mexico City and Asia this summer, thanks to her flexible work arrangement.

The Los Angeles-based marketing director is unconcerned about flight delays and cancellations even though they are "never fun."

"It does happen, so I really don't let it throw me anymore," she said.

Nearly a quarter of flights were either canceled or delayed last summer, according to flight-tracking service FlightAware.

A recent survey by consultant J.D. Power shows customer satisfaction with major airlines is down significantly. The industry is also facing heat from the Biden administration, which wants airlines to compensate passengers with cash for lengthy delays.

Rising numbers of disputes between travellers and airlines globally are driving fresh legislation and calls for tougher enforcement of existing rules to protect consumers.

'THIS IS A TEST'

U.S. Transportation Secretary Pete Buttigieg said this week Memorial Day will be a "test to the system." He said delay and cancellation rates were unacceptable last year and cannot happen again.

Overall, 42.3 million Americans are estimated to travel over the May 29 U.S. Memorial Day holiday weekend, AAA estimates.

The Federal Aviation Administration estimates nearly 313,000 flights will operate over the seven-day period ending May 30, up 4.5% from 2022 and just below 2019 pre-pandemic levels.

Demand is stronger for international trips this summer, driving up airfares to Europe and Asia to the highest level in more than five years, said online travel agency Hopper.

Carriers are performing far better this year, but a shortage of air traffic controllers has forced them to trim New York City-area flights. They are flying larger planes to compensate for fewer flights.

United CEO Scott Kirby has said the FAA needs more resources to handle the rising number of flights. Buttigieg has said the agency needs about 3,000 air traffic controllers, but added weather and airline issues are to blame for most of the problems.

United said it has hired 7,000 employees including pilots, flight attendants, ramp workers and customer service agents this year on top of 15,000 last year.

It is adding gates in New Jersey, Denver and Chicago. It also has added five new hangars worldwide to repair its planes, Enqvist said.

Rival Delta Air Lines Inc (DAL.N) has hired and trained over 25,000 employees to handle the summer travel rush. Southwest said it will operate 7% more flights compared with last year, with 15% more employees.

American Airlines (AAL.O) COO David Seymour said the airline has learned from the past. American has invested in technology that allows it to plan for weather events in advance and has tasked general managers with ensuring adequate staffing at its vendors.

"We are really laser-focused on building a plan that has resilience," he said in an interview.