Duffy held a press conference Monday afternoon, after the FAA imposed the latest of several recent ground delays at EWR. The FAA said they had been “slowing arrivals and departures” there “due to runway construction at Newark and staffing and technology issues at Philadelphia TRACON, which guides aircraft in and out of the airport.”

Duffy noted that it was the Biden administration that moved the TRACON (Terminal Radar Approach Control Facilities) from New York to Philadelphia, and said he was calling for an Office of the Inspector General investigation into this and other decisions.

However:

WASHINGTON, March 20 (Reuters) - The U.S. Federal Aviation Administration said on Wednesday it will relocate control of the Newark, New Jersey, airspace area to Philadelphia to address staffing issues and congested traffic in the New York City area. The announcement comes ahead of what could be a record summer travel season. Airlines this week forecast record travel this spring.

The move happened under the Trump administration. Either they were too inept to stop it or chose to let it happen in order to blame the Biden admin. That said, EWR is a mess even on a good day, so short staffing and runway construction would have been nasty to begin with.