"It's been an honor and a privilege to serve with our Air Force's great Airmen," Donley said in a service statement issued Friday. "Their accomplishments have been nothing short of impressive, and I'm humbled to be a part of this team."
House Armed Services Committee members will draft their version of the budget blueprint on June 5, the committee announced Thursday.
Their Senate counterparts will begin work on their version less than a week later, on June 12.
On Friday, Defense Secretary Chuck HagelChuck HagelLobbying World The US just attacked Syria. So where's Congress? Senators tear into Marines on nude photo scandal MORE praised Donley as an "invaluable adviser" during his first months as Pentagon chief and an "outstanding leader of the Air Force" since taking the service's reins in 2008.
"His leadership came during a challenging time for the Air Force, and he helped instill a culture of responsibility, initiative, and professionalism to the service," according to Hagel.
"The Air Force he leaves behind is more resilient and more respected because of his leadership and personal dedication. He will be missed," Hagel added.
The arrival of Donley and former Air Force Chief of Staff Gen. Norton Schwartz in 2008 was part of a leadership purge within the service by then-Defense Secretary Robert Gates.
Schwartz retired from the Air Force in 2012, replaced by current Chief of Staff Gen. Mark Welch.
Former Air Force Secretary Michael Wynne and Chief of Staff Gen. T. Michael Moseley were forced out of the service in the wake of a series of scandals involving the Air Force's management of the U.S. nuclear arsenal.
The accidental deployment of live nuclear weapons into a B-52 bomber during a 2007 cross-country flight from Minot Air Force Base in North Dakota to Barksdale AFB in Louisiana prompted Gates' decision to fire Wynne and Moseley.
During his tenure, Donley spearheaded efforts to revamp the safety and security of the service's nuclear weapons sector, oversaw the multibillion-dollar contract award for the Air Force's new KC-46 aerial tanker and led efforts to increase the service's role in cyberwarfare operations.