But late in the day, only 150 flights had been canceled, a relatively small number, according to website Flightaware.com. And although some travelers waited nearly two hours for flights, delays were much shorter on average.
For example, as of late afternoon New York time, flights to Charlotte Douglas International Airport were delayed an average of 22 minutes, the FAA's website showed. A flight delay of 15 minutes or less is considered on time, so a 22-minute delay is minimal by industry standards.
Flights to Florida were delayed earlier on Monday because of staffing cuts and weather, said Mark Duell, vice president of operations at FlightAware.com, a flight tracking website.
"Staffing-related delays come and go," Duell said. So far, "it's only a problem if there some other condition that's going on."
Delays at New York's major airports and in Denver were due staffing and other factors, Duell said. By contrast, Hartsfield-Jackson Atlanta International, the nation's busiest airport, and Chicago's O'Hare, reported no significant delays, the FAA said.
Industry Voices Concern
The FAA furloughs, which started Sunday, are intended to cut staffing by 10 percent to save $200 million of $637 million the agency needs to pare from its budget. Of 47,000 employees facing furloughs, which are expected to last through September, nearly 13,000 are air traffic controllers.
New York's LaGuardia and John F. Kennedy airports and Los Angeles International Airport grappled with delays of up to an hour and a half on Sunday, when the furloughs began, Duell said. The FAA said there were 400 flight delays on Sunday related to the furloughs.
Despite the improvement Monday, airlines and business advocacy groups continued to voice concern that staffing cuts would reduce corporate travel and hurt the economy.
Southwest Airlines said its estimated conservatively that furloughs would cost it $200 million a year if implemented to the full extent the FAA has outlined.
The comment was contained in a motion filed Friday by Airlines for America (A4A), a trade group of airlines. The group said it was still pressing in court for a 30-day delay of the staff cuts, after the court denied its request last week for an emergency stay of the furloughs.
American Airlines, also in an affidavit with the A4A motion, estimated furloughs would result in 582 daily flight delays and losses of $1.77 million a day.
Delta Air Lines said it might have to cancel 152 flights a day, most on regional planes operated by connection carriers, losing an estimated $575,000 a day in revenue.
Furloughs "will produce missed connections and widespread flight cancellations," the Global Business Travel Administration, a trade group, said in an open letter to FAA Administrator Michael Huerta that was distributed on Friday.
"If these disruptions unfold as predicted, business travelers will stay home."
Jean Covelli, president of The Travel Team agency in Buffalo, N.Y., said many business customers are rethinking plans for trips now that the furloughs have started.
"There is grave concern about safety," she said. "Businesses are canceling meetings. There's a whole domino effect that this is causing. I don't think it's going to get any better."
But on Monday, some major airlines said there were no flight cancellations due to the furloughs. Southwest Airlines said it expects "possible flight delays" from the staffing cuts but added it had no major problems with operations on Monday. American Airlines reported no issues other than normal ground delays.
United Airlines said the nation's air space "functioned pretty well" during the day on Sunday. But "we saw alarming pockets of degradation due to FAA staffing in Los Angeles and LaGuardia both last night and this morning," spokeswoman Megan McCarthy said in a statement on Monday. "We are concerned about how this is going to evolve and affect air travel reliability for our customers."