The Pentagon’s troubled V-22 Osprey program recorded more serious accidents in each of the last two fiscal years than the average during any of the previous eight years, U.S. congressional auditors said, highlighting a worsening record for an aircraft that’s suffered several deadly mishaps since coming into service in 2007.

The Government Accountability Office assessment, the most sweeping to date of the $56 billion program, found that the Osprey has the second most so-called catastrophic risks of any U.S. Navy aircraft, and those risks have been unresolved for an average of nine years — more than any other.

“Only the F-35 Joint Strike Fighter had more unresolved catastrophic risk assessments than the Osprey at the time of our review, and the average age of the Joint Strike Fighter’s risk assessments was 5.5 years,” the watchdog said.