Citing concern about travel to the Mediterranean, Royal Viking Line has replaced three itineraries scheduled for the Royal Viking Sun.

The new trips: from Fort Lauderdale to Montreal, April 25 to May 11; Montreal to Fort Lauderdale, May 11 to 17, and Fort Lauderdale to Copenhagen, May 27 to June 17. The Montreal-Fort Lauderdale cruise includes a visit to Baltimore on May 18, the day of the Preakness horse race, and to Charleston, S.C., on May 23 during the Spoleto Festival U.S.A.

The line has also scrapped a cruise to China on the Royal Viking Sky because of a lack of interest and substituted two 14-day voyages from San Francisco to Alaska. These trips, departing Aug. 18 and Sept. 1, will be the ship's last before retirement.

Passengers holding reservations on any canceled Sun or Sky cruise will receive a full refund as well as a credit of $1,500 a couple toward any remaining itinerary on the two vessels this year, Royal Viking said.

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Americans considering a tour to the Galapagos Islands, off Ecuador, should check with their travel agent regarding the safety specifications of the boat to be used, says a State Department advisory. It was prompted by the deaths of three Americans on a tour boat that caught fire and sank on Oct. 26.

About 20 people were asleep on the 76-foot-long wooden craft when the fire, which is believed to have started after a gas explosion in a kitchen area, broke out at 4 a.m. The advisory said the disaster pointed up the lack of safety standards on some tour vessels.