Marine Corps aviation accidents have jumped 80 percent over the past five years, a Military Times investigation has found.

From fiscal years 2013 through 2017, the total number of Marine Corps aviation accidents rose from 56 to 101 per year. Most of the increase came from Class C mishaps ― accidents that cost between $50,000 to $500,000, or resulted in lost work days due to injury.

The Marine Corps is still looking for the “why,” said Marine Corps Col. Anthony Bianca, head of aviation plans and programs.

Like the other services, the Marine Corps’ latest spike in mishaps began in 2013, the same year that the automatic budget cuts known as sequestration took effect.

With a smaller budget, the Marine Corps cut overall flying hours; its manned attack helicopters, tiltrotors, fighter jets and cargo aircraft flew 60,000 hours less in fiscal 2017 than they did in fiscal 2013, according to service data. The Corps also cut skilled maintainers as part of mandated personnel cuts and lost experienced supervisors on its flight lines.