WASHINGTON — Wanted: A senior official to oversee and manage $70 billion in annual investment spending and $300 billion over a five-year budget plan. Must be able to provide guidance, direction and supervision of purchasing plans and oversee a work force of thousands of professionals.

That description may as well be a job ad for the U.S. Air Force assistant secretary for acquisition, a position that has been vacant for nearly three-and-a-half years. But it is the one job no one seems to want.

“Let’s just say it’s been a continual challenge,” Air Force Secretary Michael Donley said on Sept. 17 when asked about the job vacancy.

It has not been for lack of trying. Donley — who is performing those duties in addition to his own — and Pentagon acquisition chief Frank Kendall have “interviewed a number of individuals” to fill “a very challenging position at a very challenging time.”

When they find people they like, they run into another problem: the salary.

“To convince those individuals — or what we think are highly qualified candidates who are in a position to come into government and to leave more lucrative compensation and intentionally cut themselves off from future employment in some respects to make this kind of a sacrifice — this is not easy,” Donley said.

The acquisition executive oversees the purchasing programs large and small, including the KC-46 tanker, F-35 joint strike fighter, Advanced Extremely High Frequency satellite, Evolved Expendable Launch Vehicle, Global Positioning System satellite and weapons. In addition, that person oversees services contracts and purchases.

The job is not an easy one. The Air Force has had a number of high-profile acquisition woes for the past decade, including a tanker lease scandal that resulted in the service’s No. 2 procurement official going to prison.

Later, the service’s top two acquisition programs — a tanker procurement and one to purchase a new combat search-and-rescue helicopter — were derailed after the Government Accountability Office found flaws in the contract awards.

“[N]obody wants to take that job,” said Marvin Sambur, who served as the Air Force acquisition chief from 2001 to 2005 and is the president and chief executive officer of Burdeshaw Associates, a Maryland-based consulting firm.

“Nobody who has any experience wants to take that job because the lessons learned here is that if you come in and you want to make change, you’re going to be penalized,” he said.

The acquisition chief’s office has been empty since Sue Payton retired in the spring of 2009. David Van Buren, who was Payton’s deputy, assumed her duties in addition to his own until March, when he stepped down. Van Buren was never officially nominated for the assistant secretary position, but filled the role.

In June, Lt. Gen. Charles Davis, the Air Force’s military deputy for acquisition, said it was “painful” not having a full-time acquisition chief and civilian deputy.

Much of the work Van Buren spearheaded to overhaul the acquisition work force has been put on hold. That includes refining the structure of the work force and training opportunities for program managers, contracting officers and engineers, along with reworking the organizational structure to account for changes in civilian manning and more, Davis said.

“It does affect our ability to manage the workload that goes with Air Force acquisition,” Donley said.