After a slew of aviation incidents in recent years, attributed largely to reduced maintenance and increased operational tempo for America’s workhorse fighters, Defense Secretary James Mattis has issued a new directive to Air Force and Navy officials: Bring America’s fighter fleets back up to an 80% readiness rating — and even more dramatically — do it within a year.

In a memo distributed in mid-September, but only recently released to the media, Mattis acknowledged that “budget constraints and shortfalls” in recent years have had a troubling effect on overall aircraft readiness. According to Mattis, who repeatedly called on lawmakers to remedy their decade-long trend of failing to pass defense budgets in a timely manner because of the diminishing effect it had on military readiness, this chronic issue has led to “systemic underperformance, overcapitalization and unrealized capacity” in America’s fighters. This is something he believes can be remedied thanks to increased defense funding for this fiscal year and a renewed emphasis on reducing maintenance costs while increasing maintenance availability for aircraft that need it.

In short, Mattis envisions cutting operating costs while increasing readiness, specifically among America’s fleets of F-35 Joint Strike Fighters, F-22 Raptors, F-16 Fighting Falcons and F/A-18 Super Hornets.

“For change to be effective and efficient, we must focus on meeting our most critical priorities first,” Mattis wrote in the memo.

Meeting that 80% mark may be easier for some of those aircraft than for others. America’s massive fleet of F-16s, for instance, sat at a 70.22% readiness rating in the last fiscal year. With more than 1,000 total F-16s in America’s inventory, bringing up that rating by ten percent will represent a significant endeavor, as each aircraft will have a notably smaller effect on the overall figure because of the size of the fleet. With that said, however, the F-16 will likely be easier to drum up readiness for than either of the fifth-generation fighters on Mattis’ list: the F-22 and F-35.

The F-35, which currently boasts an embarrassing 54.67 mission readiness rating, has been plagued by parts shortages, issues identified in testing, and squabbles between Lockheed Martin and the Pentagon about who is responsible for addressing issues like failing to prevent oxidation on the airframe where body panels are attached to the aircraft. With just a few hundred F-35s in America’s inventory, increasing the readiness rating may simply be a matter of updating earlier aircraft that were delivered before issues were identified in testing, but that will undoubtedly mean investing more money into the already bloated program.

Challenging as the F-16 and F-35 may be to bring up to an 80% readiness rating, the most difficult will likely be the F-22 Raptor. Widely seen as America’s most capable intercept fighter, the program was cut by the Obama administration as a cost-saving measure with only 180 or so aircraft produced. The F-22 now sits at a 49.01 capability rating thanks in no small part to issues with procuring parts. Most of the F-22 commercial production apparatus was cannibalized in favor of F-35 production, meaning parts for the stealthy fighter are no longer being produced in any notable quantities. In short, the F-22 is among the rarest operational fighters in the world, and getting dozens of them back into action will require a significant effort, both financially and in terms of manpower.

The F/A-18 Super Hornet already has an upgrade program underway with Boeing, though it’s unlikely enough of the jets will pass through their Block III improvement process in time to have a notable effect on readiness numbers. Ultimately, the legacy Hornets will be retired from carrier service in the Navy, replaced instead with Block II and Block III Super Hornets as all remaining Block II’s trickle their way in for upgrades. Currently, the Navy’s fleet of Super Hornets also sits at a readiness rating of below 50%.

One option that may be employed is simply cutting older aircraft with more difficult repairs from the roster entirely. It would reduce the total number of aircraft, thereby increasing readiness figures and reducing operational costs. Fewer aircraft with a higher readiness rating may not hurt the force, as the money that would be allocated to bringing some planes back from the dead could be diverted to maintaining ones that are already operational.

“For example, a squadron of 20 aircraft with a 60% availability rate is equivalent to a squadron of 15 aircraft with an 80% availability rate. You can effectively grow the force without adding planes.” Todd Harrison, an analyst with the Center for Strategic and International Studies, pointed out.

This trick, while an effective way to shift numbers, may have its own issues, however. Reducing the total number of aircraft can increase the operational requirements of each that remain — adding hours to their flight time and, in turn, increasing the maintenance costs per plane while shortening overall lifespans.

Put succinctly, it’s not impossible for the Air Force and Navy to meet Mattis’ demand… but the path to an 80% readiness rating is in no way certain.