WASHINGTON, May 11 (Reuters) -

The Federal Aviation Administration was forced to briefly

slow arriving and departing planes at New Jersey's Newark

Liberty International Airport on Sunday because of a new

telecommunications issue, the agency said.

The Philadelphia Terminal Radar Approach Control suffered a

new problem that briefly led the FAA to issue a ground stop

while it ensured redundancies were working as designed.

The FAA said operations have returned to normal. On Friday,

the Philadelphia facility suffered a 90-second radar and

telecommunications outage, the second in two weeks after a

serious outage on April 28.

The latest incidents highlight the air traffic control

network's aging infrastructure. Transportation Secretary Sean

Duffy on Thursday proposed spending billions of dollars to fix

the network over the next three to four years.

The FAA last year relocated control of the Newark

airspace to Philadelphia to address staffing and congested New

York City-area traffic.

Senate Democratic Leader Chuck Schumer of New York, said in

a press conference in New York City that the ground stop at

Newark Liberty, which is located in northern New Jersey just

miles from New York City, lasted for 45 minutes and was causing

flight delays to ripple through the day.

Noting that Sunday's problem was the third in recent

weeks, Schumer told the FAA that "the usual bureaucratic rules"

cannot dictate the pace of modernizing outdated equipment. "Fix

it. Fix it now. Do whatever it takes. Don't go by the old rules.

... Newark must be number one in their priority scale."

Newark Liberty has also been hit by runway construction, FAA

equipment outages and air traffic control staffing shortages

that prompted urgent calls from lawmakers for investigations and

new funding. Some controllers took stress leave after the April

28 outage.

Late on Friday, the FAA said it planned to meet with major

airlines on Wednesday about potential temporary cuts in flights

at Newark to address the recent major disruptions.

Duffy reiterated in an interview that aired on Sunday on

NBC's "Meet the Press" that flights need to be scaled back.

"We're having these glitches in the system. So we slow it

down and keep people safe. That's what we do," Duffy said,

pledging quick upgrades to Newark. "We're going to start to see

Newark be far more resilient in the near term."

The FAA said last week it was taking immediate steps to

address ongoing problems that have disrupted hundreds of

flights, especially from United Airlines, the largest

carrier at the airport.

United has sharply cut flights and wants the FAA to impose

new limitations on Newark flights to address ongoing delays.

The FAA said it is increasing air traffic controller

staffing, adding three new high-bandwidth telecommunications

connections, and deploying a temporary backup system to the

Philadelphia TRACON during the switch to a more reliable

fiber-optic network.

The FAA is about 3,500 air traffic controllers below

targeted staffing levels.