Travelers stranded by Hurricane Sandy are seeing service slowly restored across the Northeast. But it’ll be days before things are close to normal.

The busy Northeast travel corridor ground to a halt when the huge storm slammed into New Jersey Monday evening. Train tunnels flooded, power went out, and forecasts of high winds forced airlines to cancel thousands of flights.

Travelers and commuters were forced to cobble together ways to get home, or stay where they were.

But by Wednesday, the region’s massive network of planes, trains and buses was slowly restarting.

Flights resumed at airports, including two of New York City’s three major airports. Limited subway service is expected Thursday in the city.

Major rail service in the region remained largely suspended, however. While some commuter lines are expected back Wednesday afternoon, Amtrak’s Northeast Regional service between Newark, N.J., and Boston is suspended and so is Acela Express service for the Northeast corridor. No date is set for resumption of that service.

Air travelers stranded by Sandy are a little closer to getting home. There are limited flights at John F. Kennedy International and Newark Liberty International. The city’s third major airport, LaGuardia, is still closed as authorities assess the damage from the huge storm. Travelers hoping to fly out of New York are being told to check with their airline before heading to the airport.

Airports in Washington and Philadelphia re-opened on Tuesday.

FlightStats said the storm had caused more than 19,000 cancellations since it began, including 2,820 cancellations in North America on Wednesday.

Delta was resuming some flights at JFK on Wednesday. But other airlines, including American and Southwest, both said they won’t resume New York flights until Thursday.

LaGuardia was another story. Several airlines said they hoped to resume flying there on Thursday. But airport authorities said they don’t know yet when LaGuardia will reopen.

“There are a lot of contingencies before we can re-open at LaGuardia,” Southwest spokesman Paul Flaningan said. “It’s still barricaded at the front entrance, which makes drop-offs from taxis and buses difficult.”

Airlines continued to waive fees to change tickets for flights to New York airports. Delta and United said that anyone who planned to fly there through Saturday could change their ticket. However, the re-booked travel still had to begin by Nov. 9, giving travelers a relatively narrow window to make their trip.

American’s waiver was broader, covering New York tickets through Nov. 7, and allowing rebooked travel through Dec. 20.

Amtrak said on Wednesday that it has restored train service to Newark airport. But service to and from New York’s Penn Station was still not operating because tunnels under the Hudson and East rivers are flooded.

In Washington, the Smithsonian Institution’s museums and National Zoo are reopening after shutting their doors for two days. Smithsonian officials say all the museums and their facilities in Maryland and Virginia are in good condition. There was no damage to the collections.

At the National Zoo, officials say the animals weathered the storm with no problem.

The Smithsonian says its National Museum of the American Indian in New York remains closed, but its collection is safe.