For the past fifteen years, the government has allowed Boeing to conduct its own inspections related to many manufacturing and safety issues — and during that time, government reports, experts, and whistleblowers have issued more than a dozen warnings that the self-inspection program has led to serious production issues and contributed to two fatal crashes.

During much of that period, federal regulators shifted an ever-larger amount of the plane-certification process to Boeing, even as the plane manufacturer cut production corners and pledged to focus on “removing layers that help us be faster.”

Now a new government investigation, a whistleblower report, and aviation experts suggest the self-inspection program could have played a role in multiple recent high-altitude debacles, including a door plug blowing out of an Alaska Airlines flight over Oregon last month because four key bolts weren’t installed.