ARLINGTON, Va. — Hoping to minimize the need for involuntary separations for its most senior officers, Air Force officials have instituted a number of measures to make it easier for lieutenant colonels and colonels to retire.

In a new message to major commands, Lt. Gen. Roger Brady, Air Force deputy chief of staff for Personnel and Manpower, announced that lieutenant colonels and colonels with at least 20 years total military service and eight years of active commissioned service are eligible to apply for voluntary retirement on Sept. 1 or earlier.

The previous requirement was 10 years of commissioned service.

Officers who are not eligible for the early out include those under investigation; officers under civil charges, undergoing court-martial action or sentenced by court-martial; or those undergoing adverse personnel action, including officer grade determinations, the message said.

Officers who are facing mandatory retirement (such as those who have been passed over twice for promotion) can now also apply for retirement at an earlier date than their established mandatory retirement date, Brady's message said.

Lieutenant colonels and colonels are allowed to retire with just two years time in grade instead of three years, which was the previous requirement for active-duty officers in those ranks, the message said.

If too few lieutenant colonels and colonels decide to retire as a result of the new incentives, the Air Force may need to involuntarily separate officers in those grades, spokeswoman Jennifer Bentley said Monday.

Bentley said she did not know the number of senior officers personnel officials are hoping will take the incentives and leave the force.

Enlisted airmen were the first to feel the effects of the Air Force's "force shaping" project, with the service spending fiscal 2005 reducing the size of the active-duty population to its congressionally authorized level of 359,000.

Then iIn fiscal 2006, Air Force officials announced that the officer corps was over-manned by 4,000 airmen.

Some of that overstaffing was solved in May, when 844 lieutenants were selected for involuntary separation, which includes an honorable discharge and eligibility for programs such as Blue-to-Green (going from the Air Force and Navy to the Army).

Now, Air Force officials are working on the opposite side of the officer spectrum, the senior officers.