What to do if your trip is canceled by Sandy

• Airlines are waiving fees, which can be as much as $150, to re-book your flights
• You have until early next week in most cases to reschedule your flights
• Bus companies and Amtrak are offering refunds or vouchers for canceled trips

Thousands of flights have been canceled. Trains and buses in the Northeast have ground to a halt. Even cruise ships are stuck in port, leaving hundreds of thousands of passengers stranded, or delayed as they wait out Hurricane Sandy.

Normally, changing a reservation with an airline can cost as much as $150. But as cancellations and delays mount because of the potentially historic storm, airlines, as well as Amtrak, and some bus lines are allowing passengers to re-book without penalty, or get refunds.

The catch? It may take a while to get through to a customer service agent, and the window to take that rescheduled trip might be short.

A few tips for travelers:

Q: If my flight's been canceled, will I have to pay a fee to schedule a new trip?

A: The answer is no. By Monday afternoon, more than 10,000 flights in North America had been canceled, according to the travel tracking site FlightStats, including 1,814 on Tuesday, and carriers were allowing travelers to re-book at no extra charge. In many cases, they'll need to reschedule and take the trip by next week to avoid paying a difference in fare.

For example, United passengers who were set to fly from Sunday through Wednesday and whose flights were canceled or delayed more than two hours must re-book and travel by Nov. 7.

Q: What if I want my money back instead?

A: If your flight is canceled, you're entitled to a refund, even on a non-refundable ticket, says George Hobica, with airfarewatchdog.com. That includes any fees you may have paid for any extras, like an upgraded seat.

Q: What if I used frequent-flier loyalty miles to book my trip? Can I get those back?

A: Yes. Your miles will be redeposited, and there should be no fees attached, Hobica says.

Q: When will planes start taking off again?

A: Several airlines have said they would like to resume flights on Tuesday. But that may not be possible, with wind gusts and the threat of flooding, escalating with the storm. "We don't know what the airports will look like tomorrow,'' says Brett Snyder, president of Cranky Concierge, which offers air travel assistance. "This thing is so big, and we have a number of important airports in the Northeast that sit right on water. That's my concern. Are they really going to be able to open tomorrow or Wednesday, depending on how much flooding there is around the airports?''

Q: I was set to take Amtrak down the coast, but there's no service. What are my options?

A: Amtrak suspended all trips in the Northeast Corridor through Tuesday, including the Acela Express that is popular with business trekkers. Train passengers can get a refund, or a voucher they can use to take a future trip.

Q: What If I'd planned to take the bus along the East Coast?

A: Several bus lines, including Boltbus and Megabus, suspended service along the East Coast on Monday and Tuesday. Boltbus riders who'd already booked a trip should expect an automatic refund to their credit cards, or to their Boltbus Rewards accounts if they used loyalty points.

Megabus is planning to get back on the road after noon Tuesday, though that could change as the storm progresses. Riders who were set to travel between Sunday and Tuesday but whose bus trips were canceled can re-book a trip without paying a fee, or they can get their money back. Greyhound buses are also not running in the Northeast on Monday or Tuesday, but riders have up to a year to use their tickets.

Q: If I now have to spend an extra day in New York or, say, Washington, D.C., can I get around via local transportation?

A: It will be tough. New York's subway, rail and bus system -- the largest in North America with more than 8.5 million riders a day -- was shut down Sunday. It was only the second time in history that the entire system has come to a halt because of weather. And it was unclear when it would reopen. "Service will be restored only when it is safe to do so, after careful inspections of all equipment and tracks,'' the Metropolitan Transportation Authority said on its website. "Even with minimal damage, this is expected to be a lengthy process."

New Jersey Transit also suspended all service. And there was no getting around on Washington's Metro system, which carries roughly 1.5 million riders a day, or on Philadelphia's public transit network, which provides service to 770,000 people each day. Local transportation authorities in those areas were also uncertain when service would resume.

Q: If I'm stranded in a hotel, what are my sightseeing options?

A: Not many. Major tourist attractions up and down the East Coast were closed Monday, including Broadway theaters in New York City, Smithsonian Institution museums in Washington, and Colonial Williamsburg sights.