What to KnowU.S. airlines began canceling hundreds of flights due to the FAA’s order to reduce air traffic at the country’s busiest airports because of the government shutdown.At LAX, travelers who spoke with NBCLA reported few problems early Friday morning, but said they were concerned about their return flights. The FAA’s gradual flight reductions start with a 4% cut Friday followed by 6% Nov. 11, 8% Nov. 13 and 10% Nov. 14.Federal authorities warned earlier this week that flight delays or cancellations were possible as the U.S.

Travelers at Los Angeles International Airport expressed uncertainty Sunday morning as flight delays and cancellations mounted nationwide during the federal government shutdown.

As of Sunday morning, 109 delays were reported by the flight tracking service FlightAware at LAX, one of 40 airports that will see FAA-mandated flight cuts due to the shutdown. Fifty-one flight cancellations were reported early Sunday at LAX.

Eric Nelson was among the anxious travelers waiting for takeoff to Hawaii, part of his a packed two-week air travel itinerary that he planned long before the shutdown.

“I was freaking out,” Nelson said. “This was all booked in advance. We didn’t know about the government shutdown or anything. I have two weeks off of work and it’s one of those things where you’re like, ‘Let’s do something awesome,’ and then you’re like, ‘Oh my god, we booked six flights in 14 days.'”

Last week, the FAA said it was gradually decrease flight capacity at 40 major airports, including LAX and Ontario International Airport, starting on Friday. The gradual reductions start with a 4% cut Friday followed by 6% Nov. 11, 8% Nov. 13 and 10% Nov. 14.

Federal authorities warned that flight delays or cancellations were possible as the U.S. Department of Transportation imposes a 10% cutback on flight capacities at 40 major airports nationally. The shutdown led to staffing issues among air-traffic controllers, who are considered essential workers instructed to continue working, despite the closure and not receiving paychecks.

Air traffic controllers have gone without paychecks for nearly a month. Many have called in sick, adding to existing staffing shortages. Most are working mandatory overtime six days a week during without pay. Some some are taking second jobs to pay their bills, the National Air Traffic Controllers Association has said.

On Saturday, the union said it had delivered 1,600 handwritten letters from members to Congress calling for the shutdown to end.

As of Saturday night, U.S. airlines canceled more than 2,500 flights nationwide.

“Our flight’s scheduled, not canceled as yet,” said LAX traveler Zarita Abbott. “I’ve been before, at the gate, and seen it come on as canceled. So, I don’t count it until I’m actually on the plane.”

Five California airports are on the flight cuts list, including LAX, Ontario International Airport, San Diego International Airport, Oakland International Airport and San Francisco International Airport.

Los Angeles International Airport is among the top five busiest airfields in the nation.

Airlines have been issuing alerts to passengers to be aware of possible flight impacts.

United Airlines posted a message on its website stating, “We’re making updates to our schedule and will let you know if your flight is affected as soon as possible, but anyone flying between Nov. 6 and 13 can request a refund or reschedule for free.”

Southwest Airlines posted a notice saying the vast majority of its customers will not be affected, but said anyone with flights booked through Wednesday can adjust their travel plans at no cost, “or receive a refund if they choose not to travel, regardless of whether their flight is affected.”

Delta Air Lines also advised customers of flight reductions, and provided guidance for travelers about how they can change or cancel their flights without any financial penalties. In a statement early Friday, Delta Air Lines said all planned FAA flight cancellations for Nov. 7-9 have been completed.

Frontier Airlines stated that it expects most of its flights to operate as planned, but it will communicate with passengers whose travel plans may be impacted by the cuts.

Here are some tips for air travelers.

Other airports that will lose flights

Below, the list of airports impacted by the FAA’s decision.

ANC – Anchorage International in Alaska

ATL – Hartsfield–Jackson Atlanta International in Georgia

BOS – Boston Logan International in Massachusetts

BWI – Baltimore/Washington International in Maryland

CLT – Charlotte Douglas International in North Carolina

CVG – Cincinnati/Northern Kentucky International in Ohio

DAL – Dallas Love Field in Texas

DCA – Ronald Reagan Washington National in Virginia

DEN – Denver International in Colorado

DFW – Dallas/Fort Worth International in Texas

DTW – Detroit Metropolitan Wayne County in Michigan

EWR – Newark Liberty International in New Jersey

FLL – Fort Lauderdale–Hollywood International in Florida

HNL – Honolulu International in Hawaii

HOU – William P. Hobby (Houston Hobby) in Texas

IAD – Washington Dulles International in Virginia

IAH – George Bush Houston Intercontinental in Texas

IND – Indianapolis International in Idiana

JFK – John F. Kennedy International in New York

LAS – Harry Reid International in Las Vegas

LAX – Los Angeles International in California

LGA – LaGuardia Airport in New York

MCO – Orlando International in Florida

MDW – Chicago Midway International in Illinois

MEM – Memphis International in Tennessee

MIA – Miami International in Florida

MSP – Minneapolis–St. Paul International in Minnesota

OAK – Oakland International in California

ONT – Ontario International in California

ORD – Chicago O’Hare International in Illinois

PDX – Portland International in Oregon

PHL – Philadelphia International in Pennsylvania

PHX – Phoenix Sky Harbor International in Arizona

SAN – San Diego International in California

SDF – Louisville International in Kentucky

SEA – Seattle–Tacoma International in Washington

SFO – San Francisco International in California

SLC – Salt Lake City International in Utah

TEB – Teterboro in New Jersey

TPA – Tampa International in Florida

“United’s long-haul international flying and our hub-to-hub flying will not be impacted by this schedule reduction direction from the FAA. That’s important to maintain the integrity of our network, give impacted customers as many options as possible to resume their trip, and sustain our crew pairing systems,” wrote Scott Kirby, United Airlines CEO. “Instead, we will focus our schedule reductions on regional flying and domestic mainline flights that do not travel between our hubs.”