CHICOPEE, Mass. — Westover Air Reserve Base will lose half its C-5 cargo planes and more than 300 jobs as a result of military budget cuts, base officials announced Monday.

Eight of the 439th Airlift Wing’s massive military transport aircraft will transfer to Joint Base San Antonio-Lackland in Texas beginning next year, they said.

Air Force officials, in a statement, blamed Pentagon budget cuts for the changes.

The job cuts include the expected loss of 59 full-time enlisted personnel and 275 drilling reservists, although final numbers have yet to be determined.

Brig. Gen. Steven Vautrain, commander of the air wing at Westrover, said the changes will affect the core mission of the base.

But Westover will continue to fulfill its global military mission even after the changes, he said.

The cuts are part of an effort to slash $487 billion from the nation’s defense budget over eight years.

The C-5 fleet will be upgraded with new engines during the changeover, base officials said. The C-5 is the nation’s largest military aircraft and can carry a payload of up to 270,000 pounds a distance of up to 6,000 miles. The aircraft has been critical in recent U.S. military operations, flying nearly 75,000 hours and transporting more than 200,000 tons of cargo between Sept. 11, 2001, and Dec. 31, 2012.