BOSTON — Travelers at Boston Logan International Airport and across New England face a slow recovery after the Federal Aviation Administration lifted Friday's nationwide ground stop, U.S. Transportation Secretary Sean Duffy said at a White House briefing Friday night.

"At 8:15 tonight, Eastern Time, we've opened up the airspace," Duffy said. "Now, does that mean every flight is going to fly right now? It's going to be slow, right? So if you're watching, you're at an airport, check with your airline."

Duffy said whether flights go out Friday night depends on whether airlines have pilots and flight attendants available. Flights that can't move tonight will start moving Saturday morning, he said, adding: "It's going to take us some time to unwind what's happened this afternoon."

JetBlue cancels most remaining flights

JetBlue said it was canceling all of its remaining flights Friday evening except Europe-bound departures from Boston and New York's John F. Kennedy International Airport.

"Due to the nationwide FAA mandated ground stop, JetBlue is canceling all remaining flights this evening with the exception of Europe-bound departures from JFK and Boston," the airline said in a statement, according to CNN. "Flights already in the air are continuing to their destinations."

The airline said it expects disruptions to continue Saturday, including more cancellations, NBC News reported. JetBlue has a fee waiver in place for customers who need to change their travel plans, WSOC-TV reported.

Delays stack up at Logan

Logan had 382 delays and 216 cancellations as of 6:30 p.m., according to FlightAware data cited by WBZ-TV.

At about 5:45 p.m., Massport, which runs Logan, said "the FAA is permitting some transatlantic flights to depart Boston Logan," The Boston Globe reported.

"I've been briefed on the FAA's nationwide ground stop and am in touch with Massport about what it means for people flying in and out of Massachusetts," Massachusetts Gov. Maura Healey said in a statement, according to WBZ.

The ground stop also halted departures from Bradley International Airport in Windsor Locks and other airports across the region, The Signal reported earlier Friday.

'Old hardware' blamed

Duffy said the FAA saw instability in radar and communications at air traffic control facilities across the country at 3:36 p.m. and issued the ground stop with more than 3,500 planes in the air. All of them landed safely, he said.

He blamed the outage on the FAA's aging analog telecommunications network, saying its switches and routers "got overloaded with data" and began sending inconsistent information. "Our new IP switches did not go down. It's the old hardware that went down," Duffy said.

Homeland Security Secretary Markwayne Mullin said investigators had found no sign of a cyberattack. "It appears that this was mechanically driven. However, we're still looking," Mullin said.

Asked why the FAA wasn't better prepared, Duffy said, "I didn't anticipate that we would have an outage like this." He warned that "you will have more of these" unless Congress funds a new air traffic control system, and called for emergency funding before the end of the year.

Duffy said he expects the system to be fully operational before the Thanksgiving travel rush.