Celebrity Silhouette on the water (11:16 a.m. EDT) -- A propulsion problem is preventing Celebrity Silhouette from reaching its normal speed, forcing the cruise line to shorten select port calls through much of the fall. The line is not yet sure when the problem will be fixed.

According to Celebrity Cruises spokeswoman, Stephanie Holder, the "slight restriction" on the ship's top speed "is due to a portion of the propulsion system operating at less than optimal efficiency." Though the problem is slowing the ship down and affecting passengers' times in ports, it does not affect the maneuverability of the ship or the safety of passengers and crew.

Holder told Cruise Critic Celebrity is exploring options in regards to getting the problem fixed and will keep passengers and travel agents updated should any more changes be necessary.

Several upcoming sailings will see port calls change slightly. Two port calls, to Dubrovnik and Civitavecchia, will be shortened on the June 22, 11-night Italy & Croatia sailing, while the port of Chania (Souda) in Crete will be replaced by Katakolon in Greece on the July 15 12-night Eastern Med & Greek Isles cruise. Port calls also were shortened on the July 27, August 10 and 24 seven-night Greek Isles sailings, the August 3 and 17 seven-night Greek Isles & Turkey cruise, the September 12 11-night Eastern Med & Greek Isles sailing, the October 4 14-night Holy Land voyage, and the November 1 15-night Italian Passage sailing.

Last year, another Celebrity cruise ship, Celebrity Millennium, also had trouble with its propulsion system resulting in multiple delays, port call cancellations and culminating in the cancellation of the ship's entire Alaska season. In Millennium's case, an entire propulsion pod system needed to be replaced. It is unknown whether Celebrity Silhouette's propulsion problem is any way similar to what happened on Millennium.

--By Dori Saltzman, News Editor