Waiting for their checked bags after arriving at Baltimore-Washington International Thurgood Marshall Airport, New Orleans residents Tammy Shiner and Darleen McCarthy were already worrying about their flight home Tuesday.

“There aren’t that many carriers you can take,” Shiner said Thursday afternoon, with plans to spend the weekend visiting family in Hershey, Pennsylvania. “We’ve already thought about a Plan B.”

U.S. Transportation Secretary Sean Duffy announced earlier in the week that 40 of the nation’s busiest airports would see 10% reductions in flights in a preemptive move to maintain safe airspace amid air traffic controller shortages.

The list includes BWI and the region’s other two airports — Dulles International in Virginia and Reagan National in D.C. Flight delays and cancellations are likely coming, and airlines are scrambling to configure their reduction plans as a major holiday travel season approaches.

“It’s a federal issue, and we have to wait and see what that looks like,” said Shannetta Griffin, director and CEO of BWI and the Maryland Aviation Administration, after an event Thursday marking the airport’s 75th anniversary.

“We’ve been fortunate,” Griffin said, that BWI has not seen impacts related to the government shutdown since it began Oct. 1.

Here’s what to know as the flight reductions kick in Friday morning.

Why do airports have to reduce flights?

Out of an abundance of caution, officials said.

The U.S. already was dealing with a nationwide shortage of about 2,000 air traffic controllers, forcing many to work mandatory overtime, Duffy said Wednesday. The Federal Aviation Administration has “surged” trainees at its air traffic control academy by 20%, he said, and is offering financial incentives to older controllers to stay on the job longer.

But as the government shutdown — now the longest in U.S. history — lingers, controllers are increasingly reporting fatigue. Many are calling out of work or taking side jobs to make ends meet while they aren’t receiving a paycheck, Duffy said.

“We are seeing pressures build in a way that we don’t feel will — if we allow it to go unchecked — will allow us to continue to tell the public that we operate the safest airline system in the world,” FAA Administrator Bryan Bedford said.

Bedford and Duffy stressed that the decision was a preemptive one, not a reaction to an already unsafe situation.

Duffy highlighted that the recent fatal crash of a UPS plane in Kentucky was due to an aircraft maintenance issue, not an air traffic control one, and said his team learned from the crash over the Potomac River near Reagan airport about the importance of taking proactive safety measures.

“I want to ensure travelers that it is absolutely safe to fly in America’s skies,” Bedford said.

Some airlines have indicated they will prioritize international flights. The list includes a couple of hubs for commercial shipping companies.

How do things look at BWI and in the region?

Flight volumes vary day to day, but roughly 600 came and went from the BWI tarmac Thursday without disruptions, representing nearly 100,000 available seats, BWI spokesperson Jonathan Dean said. Slightly fewer flights are on Friday’s docket.

These numbers do not reflect any possible delays or cancellations, Dean said.

“BWI Marshall Airport appreciates travelers’ patience and understanding during this unprecedented situation,” Dean said.

A spokesperson for Southwest Airlines, which handles the lion’s share of traffic in and out of BWI, wrote in an email that, “while the vast majority of our Customers’ flights will not be disrupted,” all customers booked through Nov. 12 can change their flight at no cost or request a refund even if their flight is not impacted.

“Nothing is more important to Southwest than the Safety of our Customers and Employees. We continue to urge Congress to immediately resolve its impasse and restore the National Airspace System to its full capacity,” Southwest spokesperson Lynn Lunsford wrote.

Airlines will reach out directly to impacted customers, wrote Emily McGee, spokesperson for the Metropolitan Washington Airports Authority, which operates Dulles and Reagan, in an email.

What do I do if I have a trip planned?

“Not panic, first of all,” said Kristina Floyd, a Maryland-based travel agent at EAFB World Travel Service.

It will make for a longer day, but Floyd “cannot stress enough” the importance of getting to the airport early. Security lines have been longer than usual at many airports (Transportation Security Administration agents are federal employees, too).

It’s best to book nonstop flights when possible, Floyd said, because more layovers mean a higher likelihood of a disruption. Also, morning flights are often less likely to get delayed than later ones as disruptions mount throughout the day.

If you cannot avoid booking a flight with a layover, then limit bags as much as possible and keep essential items and a change of clothes in a carry-on. Know a little bit about the city where your layover is, too, in case you need to figure out lodging or have to turn a frustrating cancellation into an opportunity to explore a new city for a day.

Airlines are responsible for communicating with customers about delays, cancellations and changes, and it is a good idea to book directly with airlines or with an agent to get the best customer service experience, Floyd said.

If your flight is a short, regional one, consider whether you can drive or take an Amtrak train instead.

Perhaps most important, Floyd said, try to be kind and patient. The airline employees, other passengers and TSA agents working without pay don’t want this to be happening either.

Travelers can monitor www.fly.faa.gov for real-time airport impacts.

How long is this going to last?

That depends on how the air traffic controllers do in the coming days and weeks.

Additional restrictions are possible, Duffy said, if controller fatigue or callouts get worse.

Ending the government shutdown and getting controllers paid again would certainly help, but “the data will dictate what we do,” Duffy said.