Ending months of speculation, a federal advisory commission voted unanimously Friday to close the Otis Air National Guard Base on Cape Cod, a move that could jeopardize future emergency evacuations and air-sea rescues on and around the Vineyard.

State officials and congressional delegates, who lobbied heavily to keep the base open, now are vowing to fight the federal recommendations and base closure by all legal means.

"This was obviously a very disturbing development," Mark Forest, an aide to Cong. William Delahunt, said yesterday.

Otis is one of almost 200 military facilities across the country that the U.S. Department of Defense wants to close in the next few years as part of a sweeping cost-cutting measure proposed in May. The independent nine-member Base Realignment and Closure Commission charged with reviewing the Pentagon's proposal has for the most part followed its recommendations. With regard to Otis, however, the commission broke with the defense department in deciding to redeploy the fleet of F-15 fighter jets to a municipal airport in western Massachusetts instead of to New Jersey or Florida, as originally planned by the Pentagon.

The Otis air base is slated for closure by 2008.

Perhaps the largest impact the decision will have on the Vineyard is through any potential changes to the Coast Guard Air Station Cape Cod, which has shared the Massachusetts Military Reservation airfield with the Otis guardsmen since the late 1970s.

It remains unclear whether the Coast Guard can afford to operate its Cape air station without the large contributions of the Otis base. Mr. Forest said that a Coast Guard review concluded it would cost an additional $17 million every year to run the airfield alone - money the Coast Guard currently does not have.

The Coast Guard air station on the Cape is responsible for homeland security and search-and-rescue missions along the entire New England coast - from New York city to the Canadian border - and also provides emergency evacuations from the Island when weather conditions make it too difficult for Boston Medflight, a nonprofit air evacuation organization, to fly.

According to the Coast Guard, the Vineyard hospital last year called for 375 air evacuations. Almost 10 per cent of those transports - 34 cases - were handled by the Coast Guard, which has evacuated more people from the Island every year since 2000.

The Coast Guard issued a short press release after the commission vote last week, stating that it will continue to provide air support to the New England region though acknowledging that it still must determine how and from where.

"Keeping the Coast Guard air station and other units located at the Massachusetts Military Reservation remains one of various options that will be evaluated," the release said.

The Coast Guard public affairs office at the air station did not return a call for comment yesterday.

"Obviously the Coast Guard is in a very difficult position now," Mr. Forest said. "But it's a little too early to indicate what will happen or when. Right now we're all staying focused on challenging the Otis decision and examining our legal options."

Also on Friday a federal district judge ruled that the Pentagon's recommendation to close an air national guard base in Pennsylvania was null and void because it had not sought input from the state. National guard units serve both the president and the state governor, the judge said, and therefore cannot be legally removed without state input.

Massachusetts attorney general Thomas F. Reilly said this weekend that he will file a similar lawsuit because the department of defense did not consult with the state prior to recommending the Otis closure. Mr. Reilly and Gov. Mitt Romney, who are expected to run against each other for the governorship next year, said they will work together in the fight to save the Otis base.

The commission's recommendations still must be approved by Congress and President George W. Bush this fall, though at that point they can only reject the entire list and not individual base closures.