About 400 flights were delayed Sunday because of air traffic controller furloughs, the Federal Aviation Administration said, and a few more interruptions were reported Monday at Los Angeles International Airport and several East Coast airports. But because of light traffic and good weather, the nation's air travel system operated without serious problems. The FAA warned Monday that more delays are on the horizon when air traffic is heavier and severe weather puts pressure on understaffed air traffic control facilities. "Controllers will space planes farther apart so they can manage traffic with current staff, which will lead to delays at airports," the federal agency said in a statement. Although the FAA has been warning for days that budget cuts could lead to serious headaches for travelers, the sequestration delays were a small fraction of all holdups, which have averaged about 5,800 flights daily in the last 30 days. Several airports also reported flight delays Monday caused by snow, strong winds and runway maintenance. Furloughs of air traffic controllers have prompted an outcry from Washington lawmakers and litigation by pilots and airlines who say they could have been avoided. Airline workers have even started to urge frustrated passengers to pressure the FAA to reconsider the budget cuts. A Green Valley couple who were delayed in Sacramento on Sunday night on a flight to LAX said their pilot blamed the holdup on sequestration cuts. Because of the delay, the couple, Mike and Kris Vassar, missed a flight Sunday to Fiji, where they plan to help build homes with the nonprofit group Habitat for Humanity. Flight attendants and the pilots of the delayed flight urged the couple to sign an online petition to halt the furloughs. The website, DontGroundAmerica.com, was created by a trade group for the nation's airlines. "He flat out said, 'You need to do this,'" Mike Vassar, 70, said of his American Airlines pilot. They were politicking right in there. David Brooks, 64, of Los Angeles said he missed a funeral in Boston on Monday because of sequestration delays. The pilot for his flight to Phoenix was running late because of a prior delayed flight, which an airline employee said was the result of sequestration cuts. "We had to cancel our whole trip because the funeral is tonight, and we're not going to make it in time," Brooks said Monday outside the US Airways terminal at LAX. To help cut more than $600 million called for by budget sequestration, the FAA ordered air traffic controllers starting Sunday to take one furlough day in every two-week pay period. That would cut the total of the nation's nearly 15,000 air traffic controllers about 10% on any given day. By Sunday evening a few airports across the country, including LAX and New York's LaGuardia Airport and John F. Kennedy International Airport, reported delays of more than an hour because of air traffic control staff shortages. By Monday, LAX officials said, the airport was operating without major setbacks. Flights were delayed Monday an average of about 80 minutes at John F. Kennedy and LaGuardia airports, but the Port Authority of New York and New Jersey attributed those delays to construction work, high wind and other factors. "There are many reasons for delays," said Ron Marsico, a Port Authority spokesman. He declined to comment on the specific effect of furloughs. The FAA and two airline-monitoring websites showed that the nation's overall air traffic system operated close to normal for a Monday, a heavy air travel day. The exceptions were long delays attributed to air traffic control staff shortages at several airports in Florida and North Carolina. Airlines for America, the trade group for the nation's largest airlines, joined a pilots association and operators of regional carriers in a lawsuit filed Friday that asks the U.S. Court of Appeals for the District of Columbia Circuit to prevent job furloughs. But the court is not expected to consider the suit for a few weeks. The airlines and pilots groups say the furloughs will delay as many as 6,700 flights a day. In Washington, the FAA budget cuts prompted an outcry from critics of the Obama administration. "We know that the FAA has the flexibility to reduce costs elsewhere, such as contracts, travel, supplies and consultants, or to apply furloughs in a manner that better protects the most critical air traffic control facilities," said Rep. Bill Shuster (R-Pa.), chairman of the House Transportation and Infrastructure Committee. Yet rather than take this approach, the administration has made choices that appear designed to have the greatest possible impact on the traveling public. White House spokesman Jay Carney blamed Republicans for the cuts, calling the FAA furloughs "an unfortunate result" of botched budget negotiations in Congress. He said 70% of FAA's expenses are for personnel, and that the agency could not accomplish the necessary cost reductions elsewhere. Times staff writer Wes Venteicher contributed to this report.