As the Army moves to replace its aging fleet of helicopters, the service must carefully manage long-term costs as it brings the next-generation aircraft into the force, according to a recent report.

The Army’s Future Vertical Lift program is one of its six top modernization priorities, and the service is working quickly to procure the new aircraft, with plans to field the Future Attack Reconnaissance Aircraft in 2028 and the Future Long-Range Assault Aircraft in 2030.

The report, titled “Assessing the Affordability of the Army’s Future Vertical Lift Portfolio,” says the “most critical affordability issue” for the Army’s Future Vertical Lift program likely will be operation and support costs.

Operation and support costs are estimated to make up 68% of life cycle costs for rotary-wing systems, according to the Defense Department’s Cost Assessment and Program Evaluation office. On top of that, the Army will find it “challenging” to develop a new aircraft that’s as inexpensive to operate as the UH-60 Black Hawk, according to the report, which was released by the bipartisan Center for Strategic and International Studies.

The report’s authors estimate that operation and support costs for Future Vertical Lift “are likely to be more than 40 times larger” than research and development costs and more than two times larger than Future Vertical Lift production costs.

“It is a time-worn truism in discussions of defense programs that although the greatest share of attention is usually given to the development and production of weapon systems, the largest share of their costs comes in the O&S stage of the program lifecycle,” the authors write. “In the case of FVL, this observation is likely both true and perhaps uniquely relevant to FVL’s long-term success.”

The Future Attack Reconnaissance Aircraft is meant to replace the OH-58 Kiowa Warrior, which the Army retired because of budget cuts. The medium-lift Future Long-Range Assault Aircraft will eventually replace the Black Hawk.

Read the full report here.