The U.S. Department of Transportation revealed new details Wednesday about its timeline to improve Newark Liberty International Airport's air traffic control system.

Secretary Sean Duffy previously said he hoped to activate a new fiber line to improve Newark's air traffic controller communication by the end of May. He now says the Federal Aviation Administration is using an abundance of caution in its testing process to make sure all goes smoothly, and he's expecting the line to be active at the start of July if all goes well.

On the other hand, Duffy says Newark's new runway could be open a bit earlier than the target date of June 15.

Right now, the FAA is planning to add more flights per hour at Newark when that daily construction is done, but the airport will still remain below its capacity. 

FAA will reassess staffing levels this fall, Duffy says

Duffy says there are 16 controllers in training at the Philadelphia facility that handles Newark flights. They'll become fully certified at various points in the coming months, which will help staffing.

He said the FAA will reassess in October whether the staffing will allow it to ramp up the flight limits at Newark.

Duffy says despite the recent troubles, travelers shouldn't avoid Newark Liberty Airport.

"Some have asked, is the airspace safe? Is it [safe] to travel by airplane? And the answer to that is absolutely yes, of course it is, because we've slowed things down," Duffy said.

He says the flight schedule there is now manageable because the FAA has slowed the number to 56 per hour for the time being. In past years, the average has been around 77 per hour.