Struggling to finish a politically thorny task, the base-closing commission tackled a shake-up of the Air National Guard (search) on Friday after — in a setback for the Pentagon — it voted to keep open Ellsworth Air Force Base in South Dakota.

The nine-member panel endorsed the concept of restructuring the Air Guard but did not accept Defense Secretary Donald H. Rumsfeld's (search) proposal in its entirety. Instead, commissioners began to craft their own plan to shuffle personnel and aircraft around dozens of units — both large and small — in states from coast to coast.

"In parts, we concur with their recommendations. In other areas, we're making some changes," Chairman Anthony Principi (search) said.

The commissioners planned to work into the night to conclude the high-stakes decisions in the first round of U.S. military base closings and consolidations in a decade. The process has brought sighs of relief and exasperation from communities across America.

By Sept. 8, the panel must send its final report to President Bush, who can accept it, reject it or send it back for revisions. Congress also will have a chance to veto the plan in its entirety, but it has not taken that step in four previous rounds of base closings. If ultimately approved, the changes would occur over the next six years.

Air Force officials say their proposal as a whole is designed to make the service more effective by consolidating weapons systems and personnel while moving to a smaller but smarter fleet.

The Air Guard restructuring, which called for some units to lose their flying missions, has caused the most consternation and prompted some states to file lawsuits.

Work began on the Air Guard plan just as a federal judge in Pennsylvania ruled that the Pentagon lacks the authority to close an Air Guard unit in the state without Gov. Ed Rendell's approval. The judge declared the plan for that unit "null and void."

Aware of the ruling, the commission labored on anyway.

Under the Pentagon plan, units without aircraft would get other assignments such as expeditionary combat support roles. They also would retain their missions of aiding governors during statewide emergencies.

In a flurry of the biggest Air Guard decisions, the commission sided with the Pentagon in voting to shut down the Kulis Air Guard Station in Alaska.

The panel also decided to scale back — but keep open — the W.K. Kellogg Airport Air Guard Station in Michigan and the Naval Air Station Willow Grove in Pennsylvania. Commissioners took away all of the aircraft at the sites and gave the states the authority to decide the future use of those bases.

The Pennsylvania base was the subject of the federal lawsuit, but commissioners denied that was their reason for keeping the base "warm."

In May, the Pentagon proposed closing or consolidating a record 62 major military bases and 775 smaller installations to save $48.8 billion over 20 years, make the services more efficient and reposition the armed forces. The Air Guard proposal emerged quickly as the most contentious issue.

The decision to spare Ellsworth Air Force Base was a blessing for South Dakotans, who feared losing some 4,000 jobs, and a victory for Sen. John Thune (search) and the state's other politicians, who lobbied vigorously against closure. Thune, a freshman Republican, unseated then-Senate Minority Leader Tom Daschle partly on the strength of his claim that he would be better positioned to help save the base.

"This fight was not about me," Thune said just after the vote. "This whole decision was about the merits. It had nothing to do with the politics."

Famous for its Cold War-era arsenal of missiles and nuclear bombers aimed toward the Soviet Union, Ellsworth is home to half the nation's fleet of B1-B bombers and provides some 4,000 jobs for South Dakota. The Pentagon had wanted to move all the bombers to their other location, Dyess Air Force Base in Texas.

The commission found that closing Ellsworth wouldn't save any money over 20 years and actually would cost nearly $20 million to move the planes to the Texas base. The Pentagon had projected saving $1.8 billion over two decades.

The panel worried that putting all the B1-B bombers at one base would hurt force readiness. Commissioners noted that Ellsworth, located on prairie, had plenty of "unfettered airspace."

South Dakota politicians praised the panel for acting as an independent check on the Pentagon.

"They made some tough decisions. Today, they listened to the whole story," Republican Gov. Michael Rounds said. Added Sen. Tim Johnson, D-S.D., "This is a great decision for America's national security."

Rejecting another Pentagon proposal, the panel also decided to keep open Cannon Air Force Base in New Mexico. However, the base would lose all of its aircraft and face the possibility of closure in 2010. By that date, the panel said the Pentagon must find other missions for the facility or Cannon will shut down.

The vote was a compromise among commissioners who struggled to balance national security interests with fear that closing the base entirely would devastate the economy around tiny Clovis, N.M. Some commissioners said the fate of Cannon was the most difficult decision to make so far.

Gov. Bill Richardson (search), D-N.M., portrayed the outcome as a "partial victory."

The panel found that closing the base, home to four F-16 fighter squadrons, would put at least a 20 percent dent in the local economy, costing almost 5,000 jobs on the base and in the community near the New Mexico-Texas line.

Several commissioners said those stark numbers had persuaded them to keep the base open. Others advocated closure, saying the Air Force must be able to reshape itself to face future threats.