WASHINGTON ― Alabama Sen. Richard Shelby, who has served as the top Republican on defense appropriations committees and helped determine how the Pentagon spent hundreds of billions of dollars in funding, will not seek reelection next year.

“For everything, there is a season,” Shelby said in a statement. “I am grateful to the people of Alabama who have put their trust in me for more than forty years. I have been fortunate to serve in the U.S. Senate longer than any other Alabamian.”

Shelby, 86, served as chairman of the Senate appropriations committee and defense subcommittee but his role changed after Democrats won control of the Senate in recent elections.

A proponent for the littoral combat ship and expeditionary fast transport vessel, both built by Mobile shipbuilder Austal, Shelby acknowledged his advocacy on behalf of Alabama and its people.

“I have worked to enhance Alabama’s role in space exploration and the security of our nation,” he said.

Alabama is more to more than 300 aerospace companies, and aerospace manufacturing accounts for about 13,000 jobs there, according to the state’s commerce department. Mobile is home to the Airbus commercial airplanes division. Fort Rucker is home to the Army’s helicopter training center.

In addition, Huntsville is home to Redstone Arsenal, a major research, engineering and test center that houses the Pentagon’s critical missile defense and the Army’s aviation managers. It’s also home to NASA’s Marshall Space Flight Center, the U.S. government’s civilian rocketry and spacecraft propulsion research center.

Redstone was selected last month for U.S. Space Command’s future headquarters.