Of the $1 billion the department must cut if the sequester goes into effect March 1, more than $600 million would come from the Federal Aviation Administration, the agency that controls and manages the nation's skies, LaHood told reporters during a White House media briefing.
If nothing happens by March 1, domestic and defense spending will be cut by $85 billion.
The cuts mean the "vast majority" of FAA's nearly 47,000 employees will be furloughed for one day, possibly two days, during each pay period until Sept. 30, the end of the fiscal year, LaHood said. Department officials were sharing more details with unions and the airline industry, he said.
"[Safety] is our top priority and we will never allow [more than] the amount of air travel we can handle safely to take off and land, which means travelers should expect delays," LaHood said. "Flights to major cities like New York, Chicago and San Francisco and others could experience delays of up to 90 minutes during peak hours because we have fewer controllers on staff," which would ripple across the country.
Cuts also mean preventive maintenance and quick repair of runway equipment might not be possible, leading to more delays, he said.
"And once airlines see the potential impact of these furloughs, we expect that they will change their schedules and cancel flights," the outgoing transportation chief said. "So we are beginning today discussions with our unions to likely close more than 100 air traffic control towers at airports with fewer than 150,000 flight operations per year."
He said department officials also were talking with unions about eliminating midnight shifts at more than 60 towers across the country.
Asked if there were other ways to avoid the cuts he outlined, LaHood said, "[Sequester] doesn't allow for moving money around. It just does not. And it's very clear."
"This is very painful for us because it involves our employees, but it's going to be very painful for the flying public," he said.
LaHood, who oversees about 55,000 employees and has a budget of roughly $70 billion, said department lawyers were reviewing all their contracts to see what the penalties would be if they either cut or adjusted.
"We're looking at everything possible, and everything possible that's legal we will do," said
LaHood said he's spoken with appropriate congressional committees about the situation within his department should the sequester go into effect.
"And the idea that we're just doing this to create some kind of a horrific scare tactic is nonsense," he said when asked whether he was presenting the most severe consequence possible. "We are required to cut $1 billion dollars. And if more than half of our employees are at the FAA, there has to be some impact."
Concerning whether safety would be impacted because of the cuts, LaHood said, "Our people get up every day and think about safety. And we -- we think about it in a way that maybe nobody else thinks about it, certainly common, ordinary citizens. ... We will never take a back seat when it comes to safety. We just absolutely will not."