Passengers — or people who hoped they would be passengers — have been stranded across the country in recent days amid an unprecedented rash of flight delays and cancellations, particularly from Southwest Airlines.

Baltimore-Washington International Thurgood Marshall Airport, where 72% of all flights are Southwest, has been among the airports hardest-hit by the flight problems. Here’s the latest information we know about what’s going on and when the situation might be resolved.

What happened?

Thousands of flights were canceled across the United States over the holiday weekend and into this week, as severe winter weather rolled across the country. The temperatures plunged to record lows in some communities, and others, like Buffalo, were buried in snow.

Southwest canceled the largest number of flights, by far, according to the flight-tracking website FlightAware. On Tuesday, for example, 223 of Southwest’s flights through BWI Thurgood Marshall were canceled, representing 57% of its planned flights, according to FlightAware.

Wednesday wasn’t working out much better, with 203 canceled Southwest flights through BWI, representing 53% of the airline’s flights. Just two other flights were canceled at BWI as of late Wednesday morning, both from Spirit Airlines.

All of those canceled flights have left passengers stuck with nowhere to go, often separated from their checked bags. Social media was filled with photos and videos of bags and suitcases lined up at airports across the country. The hotels near BWI were filled with stranded passengers working through their alternate travel plans.

How did this happen?

When flights are canceled, that means planes and crews get stuck in the wrong locations, and it can take time for the problems to be unwound by getting planes and crews back where they’re supposed to be.

The problem is more challenging for Southwest, which largely uses a point-to-point system, sending planes directly to a destination rather than being routed through a hub as other airlines do. Other airlines can get their planes and crews back to their central hubs and resume their flight schedules more quickly.

“We ended up with flight crews and airplanes that are out of place and not in the cities that they need to be in to continue to run our operations,” Southwest official Jay McVay told reporters at Houston’s airport on Tuesday. “So that is ultimately exactly how we ended up where we are. It’s trying to get our flight crews back in the cities where they need to be to operate our flight schedule.”

He added: “We’ve been chasing our tails trying to catch up and get back to normal safely.”

The Southwest Airlines Pilots Association said in a statement that the “holiday meltdown” was not just because of the snow and cold weather, but also because the airline’s network can’t keep up with disruptions from weather or technology. The pilots’ association said it’s been pressing for upgrades to improve efficiency and resiliency, to no avail.

The pilots association said the airline needs crew scheduling software that accounts for the point-to-point flight network, better communication tools for crews to stay in touch with the airline and a “modern” labor agreement “that reflects best practices in today’s demanding operation.”

Casey Murray, a captain and pilots association president, told FOX News that the situation was “disgraceful, to say the least.”

“We’ve seen more and more meltdowns coming more frequently, with more severity. ... This is a failure of leadership. It’s a failure of IT. It’s a failure of processes,” Murray said.

What’s Southwest saying about all this?

Southwest’s CEO, Bob Jordan, posted a video on social media Tuesday night, apologizing for the problems and attempting to explain what happened.

“I want everyone who is dealing with the problems we’ve been facing — whether you haven’t been able to get to where you need to go or you’re one of our heroic employees caught up in a massive effort to stabilize the airline — to know is that we’re doing everything we can to return to a normal operation,” Jordan said at the opening of the video. “And please also hear that I am truly sorry.”

Jordan said that the situation is a “complex puzzle” that will “take several days to solve.”

“Our network is highly complex, and the operation of the airline counts on all the pieces, especially aircraft and crews, remaining in motion to where they’re planned to go,” Jordan said in the video.

Jordan said Southwest would fly a reduced schedule in the coming days to reposition planes and crews. “We’re optimistic to be back on track before next week,” he said.

Will anyone be held accountable for this mess?

The U.S. Department of Transportation posted a statement on social media on Monday, saying that officials will “examine whether cancellations were controllable and if Southwest is complying with its customer service plan.”

Transportation Secretary Pete Buttigieg said on ABC’s “Good Morning America” on Wednesday morning that the situation is “past the point” where Southwest can blame the problems solely on winter weather, noting that other airlines were running about a 4% cancellation rate, while Southwest was above 60%.

“What this indicates is a system failure and they need to make sure that these stranded passengers get to where they need to go and they’re provided adequate compensation,” Buttigieg said.

Buttigieg has been in discussions with Jordan, the Southwest CEO. Buttigieg said on CNN that USDOT can use its enforcement tools, such as fines, if necessary, to ensure that Southwest makes its passengers financially whole.

Is there any recourse for passengers?

Buttigieg said passengers should not only be refunded for missed flights, but for additional costs like hotels and meals. He said airlines should “proactively” offer to cover those costs, rather than forcing customers to request them.

On the Southwest website, the airline said all passengers with travel plans through Jan. 2 can rebook without any additional charges.

Those whose flights have been canceled can apply for refunds of their tickets as well as for additional costs, such as hotels, meals and alternate transportation. The airline promises to honor “reasonable requests for reimbursement.” Customers must submit their receipts by email.

Complaints can be filed online with the federal government.

pamela.wood@thebaltimorebanner.com