The officials called the maximum delays "an estimate... a forecast." Of the most extreme delays, Huerta said, "We think they will be infrequent."
Criticism came from all directions Thursday.
Airlines for America, which represents major U.S. airlines, said it is reviewing legal options to prevent the furloughs.
"We have consistently said, and we have three, third-party legal opinions affirming, that the FAA has the discretion to implement cuts without furloughing air taffic controllers," said spokeswoman Jean Medina.
Sen. Jerry Moran, R-Kansas, said "savings can and should be found elsewhere."
"I am baffled by the administration's continued insistence on putting its top-line message -- that we can't cut a dime without severe consequences -- before the safety and well-being of Americans."
Sen. Jay Rockefeller IV, D-West Virginia, blamed Republicans for "refusing to work" for a budget compromise, and slammed the FAA for not doing more to warn the public.
"I am deeply disappointed that the agency has failed to inform the public on how dramatically their travel plans will be impacted in the days and weeks ahead," he said. "The FAA immediately needs to do substantially more to explain the impact of sequestration on the traveling public."
Industry groups said the impact of furloughs would be far-reaching.
"For the airlines, it means significant cuts in capacity and major financial losses," said the Air Line Pilots Association, International. "For pilots, it could span from challenges getting to work to losing their jobs. For passengers, it could mean a lot of time waiting in airports and not making it to their destinations on time."
A group representing airports Thursday also warned that the FAA furloughs could impact passengers. Airports Council International - North America said it is "standing ready to assist passengers whose travel plans are disrupted by sequestration-related furloughs."
The FAA also plans to close control towers at 149 small- to medium-size airport on June 15. It postponed plans to close the airports beginning April 7 to give airports to finds alternate sources of funds for the towers.