(NewsNation) — The Federal Aviation Administration announced it is increasing oversight of Boeing, including inspecting manufacturing and production lines.

That includes those of subcontractors Spirit AeroSystems, which was responsible for manufacturing the door plug that blew off the fuselage of an Alaska Airlines flight shortly after take off.

The FAA announced new requirements for a “rigorous inspection and maintenance process” before it would unground Boeing 737 Max 9s. The agency said once it approved the process, Boeing would have to perform it on every single Max 9 before the plane could be returned to service.

The agency said the timeline for developing, approving and implementing an inspection process would be governed by safety not a desire to quickly get planes back in the air.

The FAA was already investigating Boeing after the disaster. While no passengers were killed and the plane was safely returned to Portland, passengers are still suing the company over the incident.

The door plug incident is just the latest in a series of safety issues that have plagued the Max. Boeing has faced problems with the Max’s anti-ice system, issues with fittings that attach the fuselage to the tail, improperly drilled fastener holes in the bulkhead and engine fires.

Two crashes, one in Indonesia and one in Ethiopia, also involved the Max, with Boeing paying a $2.5 billion settlement to the Justice Department and admitting it misled regulators about the safety of the Max 8.

One former Boeing senior manager told NewsNation he refuses to fly on the Max due to safety concerns and said the company needs to completely overhaul the culture to fix safety issues.