NEW YORK — Flight delays piled up across the country Monday as thousands of air traffic controllers began taking unpaid days off because of federal budget cuts, providing the most visible impact yet of Congress and the White House’s failure to agree on a long-term deficit-reduction plan.
The Federal Aviation Administration kept planes on the ground because there were not enough controllers to monitor busy air corridors. Cascading delays held up flights at some of nation’s busiest airports, including New York, Baltimore, and Washington. Many operations were more than two hours behind schedule.
Nearly a third of flights from New York’s LaGuardia International scheduled to take off before 3 p.m. were delayed 15 minutes or more, according to flight tracking service FlightAware. Last Monday, just 6 percent of LaGuardia’s flights were delayed. The situation was similar at Washington’s Reagan National Airport, in Newark, N.J., and in Philadelphia.
Some flights were late by two hours or more.
For instance, the 8 a.m. US Airways shuttle from Washington to New York pushed back from the gate six minutes early but didn’t take off until 9:58 a.m. The plane landed at 10:48 a.m. — more than two and a half hours late.
If travelers instead took Amtrak’s 8 a.m. Acela Express train from Washington, they arrived in New York at 10:42 a.m. — 4 minutes early.
Logan International Airport in Boston did not experience any significant delays, according to the Massachusetts Port Authority. The FAA site mapping staffing-related delays around the country showed Logan experiencing general delays of 15 minutes or less.
The furloughs are part of mandatory budget cuts that kicked in on March 1 after Democrats and Republicans missed a deadline to agree on a long-term deficit reduction plan.
FAA officials have said they have no choice but to furlough all 47,000 agency employees, including nearly 15,000 air traffic controllers. Each employee will lose one day of work every other week.
The FAA has said that planes will have to take off and land less frequently, so as not to overload the remaining controllers.
Critics have said the FAA could reduce its budget in other spots that wouldn’t delay travelers.
Monday is typically one of the busiest days at airports, with many business travelers setting out for a week on the road. The FAA’s controller cuts — a 10 percent reduction of its staff — went into effect Sunday but the full force wasn’t felt until Monday morning.
Some travel groups have warned that the disruptions could hurt the economy.
‘‘If these disruptions unfold as predicted, business travelers will stay home, severely impacting not only the travel industry but the economy overall,’’ the Global Business Travel Association warned the head of the FAA, Michael P. Huerta, in a letter Friday.
Deborah Seymour was one of the first fliers to face the headaches.
She was supposed to fly from Los Angles to Tucson Sunday night. First her 9:55 p.m. flight was delayed four hours. Then at 2 a.m., Southwest Airlines canceled it.
‘‘It’s pretty discouraging that Congress can’t get it together and now it’s reached the point that we can’t get on an airplane and fly,’’ Seymour said.
One factor working in fliers’ favor Monday was relatively good weather at most of the country’s major airports. A few wind gusts in New York added to some delays, but generally there were clear skies and no major storms.
Delta Air Lines said it was ‘‘disappointed’’ in the furloughs and warned travelers Monday to expect delays in the following cities: New York, Philadelphia, Fort Lauderdale, Fla., Chicago, San Francisco, Los Angeles, and San Diego.
Raymond Adams, president of the air traffic controllers union at New Jersey’s Newark airport, said on Twitter that a few flights out of Newark to the south got sent back to Newark because the Washington area air traffic control system was overwhelmed.
The FAA has also furloughed other critical employees including airline and airport safety inspectors.Katie Johnston of Globe staff contributed to this report.