Update: The hits keep coming — more than 30,000 flights disrupted since Saturday

Delays and cancellations spilled into Wednesday as a travel meltdown that began over the weekend dragged into its fifth day.

More than 700 U.S. flights had been canceled and another 1,540 delayed as of 9:50 a.m. EDT, according to flight-tracking site FlightAware. Those delays come on top of nearly 26,000 flight delays and 4,000 cancellations that have piled up since the flight woes first began Saturday. All told, that means more than 30,000 U.S. flights have been either delayed or canceled since Saturday.

The most-affected airports Wednesday were the three big New York City-area airports – LaGuardia Airport (LGA), Newark Liberty International Airport (EWR) and John F. Kennedy International Airport (JFK) – as well as Chicago's O'Hare International Airport (ORD). Those airports have been among the hardest-hit since the flight disruptions began Saturday, bringing headaches to passengers with plans to fly to, from or through those airports.

Related: These credit cards offer built-in travel protections

Though the weather forecasts were showing signs of improvement Wednesday, airlines were grappling with a huge backlog of out-of-place passengers as they tried to get back to normal.

That follows a rough Tuesday, when all three big New York-area airports were under off-and-on ground stops throughout the day.

Delta Air Lines has issued a weather waiver for the New York region through June 28. Other airlines may similarly be willing to help you rebook if you are worried about your upcoming flights. United Airlines also has a weather waiver in place that it's extended multiple times as thunderstorms wreak havoc on airline schedules for multiple days.

Be sure to see our complete guide to what to do if your flight is delayed or canceled.

The good news is that things have improved slightly since the weekend after a mix of severe weather and an acute equipment outage in the Washington, D.C., area (which has since been fixed) briefly shut down several major airports. At one point Sunday, most major airports in the Northeast were operating with a ground stop, halting departing traffic bound for these specific airports.

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As we've seen time and again, even a short pause in operations is enough to bring an airline to a halt these days. The good news is that no single airline is in full-blown meltdown mode, and delays seem far more abundant than cancellations.

Meanwhile, the blame game continues over who is at fault.

United Airlines said the Federal Aviation Administration holds much of the blame. CEO Scott Kirby said thunderstorms wouldn't normally lead to such a domino effect on other flights. He said the FAA cut the number of flights into and out of Newark over the weekend, compounding the problems. "I'm also frustrated that the FAA frankly failed us this weekend," Kirby wrote in a letter to employees obtained by The Points Guy, thanking them for working under the extreme conditions. The Wall Street Journal first reported on that memo.

Kirby says he will talk to the FAA and the Department of Transportation about preventing similar incidents this summer.

On Sunday, FlightAware data showed that the four biggest U.S. airlines delayed between 35% and 40% of their flights but canceled just around 5% of their operations. Airlines largely build their schedules assuming there will be good weather, so any disruption is bound to throw off a perfectly planned schedule.

Since the coronavirus pandemic began, airlines have had trouble recovering from even the smallest disruption in a localized part of their network. This weekend, major metro areas were experiencing bad weather, but no carrier has suffered a large-scale meltdown yet.

While it's certainly possible that operations might get worse this week (and later this summer), carriers have had a few years to prepare for what's poised to be one of the busiest summer travel seasons on record.

Despite warnings of longer-than-usual hold times, airline call centers were faring better than expected Monday, given the irregular operations. American Airlines offered callbacks within 36 to 50 minutes, and Delta quoted a 56-minute hold. Top-tier elite flyers have been able to get in touch with representatives immediately, TPG tests showed.

Related: How to reach airline customer service quickly

Perhaps the biggest issue this summer is that getting rebooked could take days when things go wrong. Flights are operating with record load factors, so there simply aren't many seats available for rebooking.

For instance, Sunday's slew of cancellations in popular routes — like New York to Chicago and New York to South Florida — caused most flights to sell out until Wednesday. Any remaining seats were only available for walk-up fares topping $1,000 in some cases.

Without any spare seats available, some flyers, especially families with multiple travelers, are also finding that it's taking a few days to rebook.

For now, all eyes turn to the upcoming Fourth of July holiday weekend, which could be the busiest of the entire summer travel season.

United Airlines says that nearly 5 million people are expected to fly with the carrier between Friday, June 30, and Saturday, July 9. Bookings are up about 12% from last year and are nearly equal to pre-pandemic levels.

Friday, June 30, will be the busiest day to fly with United — more than 500,000 customers are expected to take to the skies with the airline that day.

Additional reporting by Ben Mutzabaugh and Clint Henderson.

Related reading:

• Key travel tips you need to know — whether you're a beginner or an expert traveler
• 6 real-life strategies you can use when your flight is canceled or delayed
• Maximize your airfare: The best credit cards for booking flights
• What you can ask from an airline after a delayed or canceled flight