On some routes Monday, it was actually faster to take ground transportation. 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 almost 10 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. — four minutes early.
Normally, there are 10 air traffic controllers at a regional facility handling arrivals for Los Angeles International Airport. On Sunday night, there were just seven, according to Mike Foote, a local union president with the National Air Traffic Controllers Association. A low layer of clouds late compounded the situation.
In such weather, two controllers do nothing but watch planes as they descend below 15,000 feet to ensure they don't veer off course. That allows 68 to 70 planes to land each hour. Because of the furloughs, there were no controllers to do that Sunday, dropping the arrival rate to 42 planes an hour, Foote said.
United Airlines said there were "alarming pockets" of delays and warned that if a solution isn't found, the problem could "affect air travel reliability for our customers."
Delta Air Lines cautioned travelers to expect delays in New York, Philadelphia, Fort Lauderdale, Fla., Chicago, San Francisco, Los Angeles and San Diego.
Many flights heading to Florida were seeing delays of up to an hour. By late Monday, delays into Los Angeles were expected to average three hours.
Having just one fewer controller to handle arrivals to Newark Liberty International Airport can result in the airport being unable to use a relief runway to handle peak traffic, reducing arrivals by about 15 percent, said Dean Iacopelli, a union official at an FAA regional facility for New York's airports.
"It is not just telling one out of 10 people to stay home and so one out of 10 planes get delayed. It's much more complicated that," Iacopelli said.
Prior to the furloughs, if a controller called in sick, there were enough people to take on the extra work, Iacopelli said, or somebody could be asked to work overtime. Now that isn't possible.
The FAA has also furloughed other critical employees, including airline and airport safety inspectors.
In a letter to the FAA Friday, Delta general counsel Ben Hirst asked the agency to reconsider the furloughs, saying it could make the cuts elsewhere and transfer funds from "non-safety activities" to support the FAA's "core mission of efficiently managing the nation's airspace."
Two airline trade associations and the nation's largest pilots union filed a lawsuit Friday asking the U.S. Court of Appeals to halt the furloughs. No hearing date has been set.
The two airline associations — Airlines for America, which represents major carriers, and the Regional Airline Association — are asking the court to place a moratorium on enforcement of the Department of Transportation's three-hour limit on the length of time airlines can keep passengers waiting inside planes on the tarmac without giving them the opportunity to return to a terminal.
Airlines can be fined as much as $27,500 per passenger for violating the limit. The Transportation Department said it is reviewing the industry's request.
Associated Press writers Joan Lowy in Washington and Christopher Weber in Los Angeles contributed to this report.
Scott Mayerowitz can be reached at http://twitter.com/GlobeTrotScott .