The problems that disrupted flights at New Jersey's largest airport this spring could be repeated anywhere across the country, so Transportation Secretary Sean Duffy is trying to sell Congress on his plan to overhaul the nation's air traffic control system that will cost "tens of billions."

Duffy provided an update Wednesday on the repairs and staffing efforts that are underway to help eliminate the problems affecting Newark Liberty International Airport, which has been running more smoothly in the past few weeks since the airlines started to cut the number of flights they operate there.

And Duffy emphasized that the Newark radar outages and air traffic control shortage are a prime example of why the antiquated system needs to be improved.

"I'm concerned that we could have more Newarks. And again, why it's so important that we actually begin this build with the money that Congress is going to send us," he said.

Duffy still wouldn't give a price tag of his expansive overhaul of the air traffic control system that he said is clearly needed after the deadly midair collision over Washington, D.C., in January that killed 67 people and all the problems affecting Newark this spring. But he said the $12.5 billion the House included President Donald Trump's massive bill won't be enough because "it's going to be tens of billions of dollars."

Duffy has been meeting privately with lawmakers since he unveiled the plan. But he said he wants to let Congress "do the dance the way the Congress dances" to develop a plan to pay for the program.

The problems that led to hundreds of cancellations and delays at Newark do seem to have improved since the Federal Aviation Administration limited the number of flights at the airport so they could handle it with the number of controllers available. The already short-staffed air traffic control facility in Philadelphia that directs planes in and out of Newark lost five controllers to trauma leave after the first radar and communications outage on April 28 and another one is out on medical leave.

That left the facility with only 16 certified controllers and five supervisors. But Duffy said there are another 16 experienced controllers in training that he hopes will start to get certified between now and October.

That is an example of how the FAA remains about 3,000 short on the number of air traffic controllers it wants, so Duffy has also tried to speed up the hiring and training process while offering incentives to keep experienced controllers from retiring early.

The FAA has said that it expects to be able to bump up the number of flights daily in Newark to 34 arrivals and 34 departures once a runway construction project is completed in mid-June. That is also about the time that some of the controllers on a 45-day trauma leave might be scheduled to return. The FAA will revisit the limits in October because it hopes to have more controllers trained by then.

The government also upgraded the software at the air traffic control facility after a second radar outage on May 9. That helped prevent a repeat problem on May 11.

The FAA is also working on the telecommunications problems. Duffy said Verizon worked quickly to install a new fiber optic line between Philadelphia and New York over the past month, but the FAA wants to thoroughly test it out before switching over, so that likely won't be available until July. After that, the FAA plans to also improve the lines between New York and the Newark airport because some of them are still copper wires.

"Clearly something wasn't going right when we experienced these outages," acting FAA administrator Chris Rocheleau said. "Right now, part of this effort, part of this initiative, is to ensure we're acting with decisiveness, right -- with focus -- to make sure the lines get in, to make sure those redundancies are put in, to make sure the controllers have the tools they need to make the system safe, to operate safely."

In the meantime, Duffy said it would be a good idea for pilots to brush up on their procedures of how to handle an outage because they can happen. In addition to the problems in Newark, controllers in Denver lost their radios for a couple minutes earlier this month. Duffy said there were also several other outages affecting Newark last year that didn't get public attention.

"We have to look at the real world around us and some of the issues that come up and make sure we are brushed up and ready to go, should there be a brief outage," Duffy said. "And again, that there's a lot of redundancy and a lot of procedures that keep people safe should this happen."