The United States Federal Aviation Administration (FAA) agreed to pay $90,000 to an aviation safety inspector who faced retaliation for raising concerns about unqualified flight safety inspectors, a US agency said on Monday.

The US Office of Special Counsel (OSC) said the whistle-blower aviation employee disclosed flight inspectors were certifying pilots and conducting safety "check rides" even though they lacked the necessary formal training and certifications.

The OSC, an office that reviews whistle-blower allegations, said the FAA's Office of Audit & Evaluation "substantiated the whistle-blower's allegations, calling into question the operational review of several aircraft, including the Boeing 737 MAX and the Gulfstream VII".

The FAA said it "takes all whistle-blower allegations seriously and does not tolerate retaliation against those who raise safety concerns".

Boeing Co declined to comment. Gulfstream, a unit of General Dynamics Corp, said the G500 and G600 were certified by the FAA in 2018 and 2019 and have flown more than 5,000 hours since. "We are confident we surpassed the requirements necessary to successfully certify the pilot training program for the G500 and G600," a company spokeswoman said.

In September, the OSC said the FAA appeared to have been "misleading in their portrayal of FAA employee training and competency" in providing Congress information about some safety inspectors who were involved in assessing training requirements for the Boeing 737 MAX.

The 737 MAX has been grounded since March after crashes in Indonesia and Ethiopia killed a combined 346 people. The certification process for the MAX has come under scrutiny.

The FAA said in September that all of "the Aviation Safety Inspectors who participated in the evaluation of the Boeing 737 MAX were fully qualified for those activities". The agency denied misleading Congress.

The FAA found that after disclosing the problem, "the whistle-blower faced retaliation. The whistle-blower decided to take a new position in another city in order to escape what he believed was pervasive harassment," the OSC said. "After he made the disclosures, his managers also allegedly removed his duties and denied training requests, flight certifications and job training opportunities."

The OSC said during the investigation, the whistle-blower's then-manager retired, so it did not seek disciplinary action.

The head of the OSC, Henry Kerner, said in September the "FAA's failure to ensure safety inspector competency for these aircraft puts the flying public at risk".