A second whistleblower to raise concerns about the safety of Boeing’s aircrafts has died.

Joshua Dean – a former quality auditor for Spirit Aero-Systems – died Tuesday at the age of 45.

Before his death, he was one of the initial whistleblowers who alleged that Spirit’s leadership failed to acknowledge the deficiencies in Boeing’s 737 Max airliners.

Dean’s death occurred less than two months after another Boeing-linked whistleblower was found dead.