Family stands to lose nearly $6,000 in airfare and hotel costs after they were bumped from an overbooked cruise ship

• Royal Caribbean International and Celebrity Cruises have overbooked multiple ships in recent months.

• Some passengers' trips are being canceled or rescheduled with varying compensation as a result.

• One customer said she may lose nearly $6,000 after being bumped from an overbooked cruise.

Cruises are back in full swing this summer, but the industry's resurgence has introduced a new headache for passengers (beyond fiercer competition for pool chairs): overbooked ships.

Royal Caribbean International and Celebrity Cruises have seen a spate of overbooked ships in recent months, the Wall Street Journal reported Thursday. The Wonder of the Seas, the world's largest cruise ship, has been overbooked three times in the past six months, according to industry blog Cruise Hive.

Just like airlines, cruise lines may sell more suites than they have physically available as a buffer for last-minute cancellations. When the math doesn't work out, cruise lines will offer guests varying compensation to entice them to change their travel plans, hopefully preventing the need to forcibly cancel guests' reservations.

On the rare occasion that not enough people voluntarily reschedule their trip, some unlucky guests may receive the dreaded email that their trip has been canceled.

That's what happened to 68-year-old Diane Gainey and her family, who were notified at the end of last month that their September cruise onboard the Celebrity Millennium had been oversold. After she declined to reschedule the 12-night cruise from Japan, she was informed by her travel agent that Celebrity Cruises had canceled her sailing.

A Celebrity Cruises spokesperson said the company continuously monitors their sailings to prevent disruptions to guests' travel plans. To avoid potential oversell issues, the cruise line offers guests the ability to voluntarily choose another sailing if their plans are flexible and onboard credit to use on their next vacation.

Royal Caribbean International and Celebrity Cruises did not respond to questions about their recent overbooking incidents, how many reservations have been forcibly canceled as a result, or their compensation guidelines for airfare and lodging not booked directly through the cruise line.

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With her September cruise canceled, Gainey was left with two options: reschedule the three-person, $8,000 reservation to a similar cruise next year or cancel the trip and receive a full refund. Celebrity offered to cover $500 worth of extra costs such as airfare, emails show.

But in order to travel from the US to Tokyo, the cruise ship's port of departure, Gainey had already spent nearly $6,000 on airfare and hotel reservations, according to receipts viewed by Insider.

Her family's flights are non-refundable and non-transferable, she said, adding that they are unable to change their flights to the 2024 dates of the next available cruise because the airline's schedule is not available that far in advance.

"I'm really stuck in limbo," she told Insider. "I don't even know if I'll be alive in a year in a half."

Have you been a passenger on an overbooked or overcrowded cruise ship? Email this reporter at htowey@insider.com

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