LOS ANGELES (KABC) — Los Angeles International Airport (LAX) and Ontario International Airport (ONT) are on the list of 40 major airports across the country where the Federal Aviation Administration (FAA) will reduce flight capacity by 10%.
The FAA previously said the announcement would be made on Thursday, but ABC News exclusively obtained the list on Wednesday night.
No state will feel the impact more than California. San Diego International Airport (SAN), OAK Oakland International Airport (OAK) and SFO San Francisco International Airport (SFO) also made the list, bringing the total number of California airports impacted to five.
The decision to reduce flight capacity over air traffic safety concerns could ground as many as 4,500 flights per day, impacting hundreds of thousands of passengers. It happens as the longest government shutdown in history continues with no end in sight.
FULL LIST: FAA to cut thousands of flights a day starting Friday due to shutdown: List of airports here
The restrictions will go into effect Friday morning, FAA Administrator Bryan Bedford and Transportation Secretary Sean Duffy said.
ABC News obtained the list of airports, which includes Atlanta's Hartsfield-Jackson, Boston Logan, all three New York City-area airports, Chicago O'Hare and many others. Sources said the cuts could start as early as Thursday.
A source told ABC News that the flight reductions will start at 4% on Friday and work up to 10%. The flights impacted by these reductions are scheduled during the hours of 6 a.m. to 10 p.m.
"We have decided that a 10% reduction in scheduled capacity will be appropriate to continue to take the pressure off our controllers," Bedford said.
International flights are exempt from the cuts, the source said, adding that a final list of airports and the FAA order with details is still in the works and is expected to be issued Thursday.
"Our sole role is to make sure that we keep this airspace as safe as possible. Reduction in capacity at 40 of our locations. This is not based on light airline travel locations. This is about where the pressure is and how to really deviate the pressure," Bedford said during the press conference on Wednesday.
The already understaffed air traffic controllers are overworked and now six weeks without government pay. Now, the FAA says they can no longer safely manage the airspace as it is.
"Well, I think it's going to lead to more cancellations, but we're going to work with the airlines to do this in a systematic way," Duffy said.
The announcement comes after Duffy said earlier this week that the FAA will be forced to shut down the airspace in some areas if the shutdown continues into next week.
United Airlines released a statement on the reduction, saying long-haul international and hub-to-hub flights will not be impacted.
The airline said customers looking for a refund on any flight can get one, even if flying basic economy or with a non-refundable ticket. The company will use its app, as well as email and push notifications, to update customers, according to the statement.
Meanwhile, in a post on LinkedIn, Frontier CEO Barry Biffle suggested booking a backup ticket on another airline. He advised travelers should book a higher-tier ticket so they can reuse the ticket value or get a credit.
The forthcoming reduction in capacity marks an unprecedented move by the FAA and the Department of Transportation. Bedford said he has never seen this happen before in his 35-year career.
Both Bedford and Duffy emphasized that the decision to cut down flights is a proactive measure based on data the department has reviewed, and the staffing pressures anticipated to grow during the shutdown. Duffy said the action is being taken to "reduce the risk profile in the national airspace."
At LAX, delays were already starting to light up on Wednesday night, and passengers were making alternative plans.
"You know, I haven't even booked a return trip because of that," traveler Nicholas Hefter said.
"I was probably going to have some issues coming back from London, so I figured, you know what, let me just avoid it and stay home and cancel that meeting," Owen Igbinosun said.
Now, three weeks out from what's historically the busiest travel day of the year, air traffic is already buckling under the pressure of the longest government shutdown ever.
"Today, people seem very tolerant. Give it a few weeks, give it the Thanksgiving holidays, we'll see how it looks," traveler William Trout said.
ABC News contributed to this report.

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