Entering what is usually the busiest month at BWI Marshall Airport, airline delays and cancellations are causing headaches for travelers here and across the United States. Even as the number of people flying bounces back to pre-pandemic levels amid loosened travel restrictions, a mix of bad weather and pilot and other staffing shortages is upending plans and sending prices soaring.

On Wednesday, according to flight-tracking website FlightAware, 5,725 flights were delayed within, into or out of the U.S., while 639 U.S. flights were canceled. At Baltimore/Washington International Thurgood Marshall Airport, about a quarter of departing flights were delayed Wednesday, but only about 1% were canceled, the website’s data shows.Bolton Hill resident Stephanie Streb, her husband and their two children, ages 10 and 12, were stuck in Toronto on the return leg of a trip from France. Multiple delays and cancellations since June 25 turned two connecting flights into five. The family had tried unsuccessfully since June 26 to find a flight or even a rental car back to the Baltimore-Washington area. Four flights booked out of Toronto since June 26 were all canceled.

The family finally gave up trying to book a flight, took a taxi to the border, crossed the border on foot and took a taxi to the Buffalo, New York, airport to rent a car. They arrived home Wednesday.

Their problems started with striking airline workers and staffing shortages in Europe, Streb said, describing airports there and in Toronto as overrun with piles of luggage and long lines of travelers competing to rebook flights canceled at the gates.

“There’s this huge influx of people trying to travel and they just don’t have the security staff, they don’t have the flight staff, they don’t have the pilots,” she said. “It’s just one thing after another. We missed our connecting flight to D.C., which then just set us back days. It’s this constant, cascading series of bad events.”

Government air travel statistics show that the problems of fewer on-time flights and more cancellations go back several months.

At BWI, according to the most recent U.S. Department of Transportation report, the share of on-time flights dropped to 72% in April from nearly 88% a year earlier, while delayed flights doubled, to 8% from less than 4% in April 2021. Canceled flights increased to 2.5% in April from less than 1% in April 2021, according to the Bureau of Transportation Statistics data.

BWI’s performance in April largely mirrored those for all major airports as a whole. Canceled flights at the airport in Anne Arundel County hit a high this year of 10% in January.

In April, the flight delay rates for BWI’s three biggest carriers were Southwest, 7.7%; Spirit, nearly 10%, and Delta, 8.3%. Cancellation rates by carrier, meanwhile, ranged from less than 1% to as high as 8%, for Spirit.

Southwest Airlines, which operates at 121 airports in 11 countries, defended its performance and said it plans to operate its peak, summer flight schedule.

“We’ve been hard at work to prepare for this busy season and have taken numerous steps aimed toward supporting operational performance,” the company said in an email.

The airline said it has hired more than 14,500 employees in the past year and plans to hire an additional 10,000 this year.

Since the beginning of May, the airline said it “has posted solid operational reliability in terms of flight completions and a cancellation rate among the lowest of ranked carriers,” the email said.

But that may be of little comfort to those passengers who’ve been subjected to abrupt changes in travel plans or left stranded.

When Anne Corey’s Southwest flight returning June 26 to BWI was canceled abruptly during a weekend trip to Charleston, South Carolina, Corey said she was forced to buy a new ticket on a different airline to get home.

The Howard County high school math teacher needed to be back the next day to teach summer school.

“I had to scramble. I spent about $360 on another flight through American and that one only brought me to Dulles,” Corey said. “So, I had to fly to Dulles and then take an Uber from Dulles to Baltimore.”

Corey is planning to ask Southwest for reimbursement, or at least credit on a future flight.

“That was already an expensive trip that was made a bit more expensive,” she said.

Evan Stewart, a 36-year-old Baltimore resident, had a similar Southwest experience.

Stewart flew Southwest to Denver for a high school friend’s wedding the last weekend of May, booking the trip early in the year.

Between that time and the trip, the airline canceled and rescheduled the flights several times, at one time moving Stewart to a return flight on Monday of that weekend, a day he was scheduled to work.

He straightened that out, or so he thought. But while in Denver on the day after his friend’s wedding, the airline canceled the flight home. He scrambled to find alternate flights, but had no luck.

He eventually rebooked for the next day.

Since then, Stewart, who works in brewery sales and usually flies several times a year, said he’s decided to either put off trips until fall or drive instead of flying.

“I basically at this point am trying to avoid it where possible,” he said. “The time I’m willing to drive, rather than fly, has gotten bigger in the past six months.”

July is typically BWI’s busiest month and the peak summer travel season is in full swing.

Jonathan Dean, an airport spokesman, urges passengers to be mindful of that when traveling over the Fourth of July weekend and the rest of the summer and consider taking morning flights if possible.

“That provides the most flexibility in case of weather or other complications,” he said.

Travelers also might want to consider flying a day early if they’re heading to special events such as weddings, he said. And as always, passengers should arrive early enough to park, check in, and go through security screening.

Passenger traffic at BWI has surged back after pandemic lows, Dean said. On June 23, departing passenger traffic at the airport hit a new high for the pandemic of 31,436, surpassing the Wednesday before Thanksgiving 2021 as the airport’s busiest day since the start of the pandemic.

Bob Mann, an airline industry analyst with Port Washington, New York-based R.W. Mann & Co. said the industry is facing a perfect storm of peak summer demand, the usual weather delays and airlines’ severe miscalculations planning to handle capacity. The pilot shortage has been complicated by longer-than-expected time to hire and rehire, train, retrain and secure background checks.

“It’s a planning problem. It’s a resource re-creation problem, and it was triggered by both age-related retirements, some buyouts and by the need to rehire people to go with the demand that has reappeared as the pandemic is winding down,” Mann said.

Like Southwest, other U.S. air carriers say they are taking steps to improve summer operations.

A trade group said last week that airlines have scaled back on June-through-August flights by 15%, increased hiring and training for flight crew, customer service and other airport staff, and allowed more flexibility in passenger itinerary changes. Aiming to keep flights on track, carriers such as United Airlines, Delta Air Lines, JetBlue and Alaska Airlineshave announced summer schedule cutbacks at some airports.

But some problems go beyond the airlines’ control, the group Airlines for America said in a June 24 letter to U.S. Transportation Secretary Pete Buttigieg. The group’s CEO, Nicholas E. Calio, noted problems with air traffic controller staffing, saying such issues led to at least a third of one of the group’s members’ recent cancellations.

The trade group asked for a meeting with Buttigieg “to discuss how we can work together to better understand FAA’s controller staffing plan for the upcoming July 4th weekend and summer travel season.”

The Federal Aviation Administration said in a statement Wednesday that it has acted on issues raised by airlines, including placing more controllers in high-demand areas.

“People expect when they buy an airline ticket that they’ll get where they need to go safely, efficiently, reliably and affordably,” the FAA statement said. “After receiving $54 billion in pandemic relief to help save the airlines from mass layoffs and bankruptcy, the American people deserve to have their expectations met.”

For many travelers, it may be a summer to forget.

Columbia resident Laura Williams, her husband and their two teenagers just returned to Baltimore from what was supposed to be an all-inclusive trip to the Dominican Republic that never happened.

The family flew out of BWI on June 21 and had an overnight layover in Miami, where they learned their American Airlines flight to their island destination the next day was canceled.

No flights were available until four days later, which would have been toward the end of their planned stay. Her family then was booked on a flight home the next day. But that flight also was canceled at the last minute, for weather reasons.

Fearing further flight cancellations, the family decided to rent a van and spent two days driving home. But the experience got worse. Williams said the travel insurance company said the “trip interruption coverage” may not apply because they weren’t “delayed.” And instead of the full refund they requested, American Airlines offered a $125 credit for future travel, which Williams called a pittance compared with the cost of flights for four people.

American Airlines did not respond to a request for comment.

“Our entire vacation is gone. It’s totally gone,” Williams said. “I would imagine July 4th coming up is going to be a hot mess for a lot of people.”