The Air Force is cutting the number of career fields eligible for selective re-enlistment bonuses — worth up to $90,000 — by nearly one-third in 2017, the service announced Thursday.

But the Air Force is also greatly expanding re-enlistment bonus eligibility this year for some of its most senior enlisted airmen, in some of the most in-demand career fields.

And much more money will likely be handed out in 2017 to entice airmen to sign up for another enlistment. The Air Force has budgeted $250 million for this year's bonuses, up from the $226 million budgeted last year. 

Last year, in a major expansion of the SRB program, the Air Force offered bonuses to airmen in 117 career fields. But the Air Force on Thursday said that, effective immediately, the number of eligible Air Force specialty codes is dropping to 80.

"The SRB program is designed to be a flexible and responsive force management tool," Col. Rob Romer, chief of the Air Force's military force policy division, said in an email to Air Force Times. "The SRB program supports the Air Force's growth by focusing on AFSCs in need of keeping experienced airmen and those that are most critically undermanned. As we grow our force, it is critical to retain experience to maintain readiness and train our new airmen."

Fifty AFSCs have dropped off this year's SRB list, including in-flight refueling; cryptologic language analysts speaking Persian and Pashto; airborne crypto language analysts speaking Persian, Pashto and Urdu; aircraft structural maintenance; fuels, missile and space system maintenance; vehicle operations; munitions systems and aircraft armament systems; among dozens of others.

But there are also 13 new AFSCs added to the list this year, replacing some of those dropped off. For example, 1N4X1B fusion analysts-analysis and production are now off the list and replaced by 1N4X1A fusion analyst-digital network analysts. And the Air Force has added Arabic-speaking crypto language analysts, as well as nuclear weapons airmen, cardiopulmonary lab airmen and several types of bomber maintainers.

The Air Force also is upping opportunities for senior enlisted airmen with between 18 and 20 years of service to get a re-enlistment bonus. Last year, four AFSCs allowed those airmen to get re-enlistment bonuses — combat controllers, Tactical Air Control Party airmen, pararescuemen, and explosive ordnance disposal airmen.

This year, however, 17 AFSCs are eligible for re-enlistment bonuses for airmen with 18 to 20 years of service. The newly-eligible career fields are airborne crypto language analysts speaking Arabic and Chinese; crypto language analysts speaking Arabic; cyber warfare operations; survival, evasion, resistance and escape; special operations weather; remotely-piloted aircraft maintenance craftsmen; helicopter and tiltrotor aircraft maintenance craftsmen; nondestructive inspection; cardiopulmonary lab; aerospace medical service independent duty medical technicians; and chaplain assistants, in addition to the four eligible last year.

"The Air Force weighed manning, experience levels, retention trends and training costs across all Air Force specialty codes to determine the FY17 selective re-enlistment bonus list," Romer said. "The 13 additions to the FY17 SRB list represent critical and emerging career fields with high operations demands and low manning or retention, such as maintenance and intelligence, surveillance and reconnaissance. The AFSCs removed from the SRB list no longer met the highest need based on our analysis of manning, retention, retention trends, or training costs."

Zone A airmen, or those with between 17 months and six years of service, get half of their bonus paid up front in a lump sum, and the rest paid out in equal annual installments for the rest of their re-enlistments. Zone B airmen with between six and 10 years of service get 75 percent paid up front, and the rest paid one year later.

Zone C and D airmen — those with either 10 to 14 years of service or 18 to 20 years of service — get all their money paid out in a lump sum.

The list of career fields eligible for selective re-enlistment bonuses can be found

.