The Federal Aviation Administration said Wednesday that an initial round of inspections of 40 Boeing 737 Max 9 planes had been completed, but that those planes and dozens of other Max 9 planes would remain grounded while the agency finalized an inspection process for them.

On Friday, the FAA announced it would require 40 inspections before approving new inspection and maintenance instructions developed by Boeing. The agency grounded 171 Max 9 planes this month after a door panel flew off on an Alaska Airlines flight while climbing after takeoff from Portland, Oregon, forcing an emergency landing.

In its statement Wednesday, the FAA said it would review data from the 40 inspections and that 737 Max 9 planes with door panels would remain grounded until the agency approved instructions for airlines to inspect the planes. The door panels go where an emergency exit door would be in a different configuration of the plane.

“The safety of the flying public, not speed, will determine the timeline for returning these aircraft to service,” the agency said in the statement.

Last week, the FAA announced it was investigating whether Boeing failed to ensure the 737 Max 9 was safe and conformed to the agency’s approved design. The incident involving the Alaska Airlines flight did not result in serious injuries, but could have been much more serious if it had occurred when the plane was at its cruising altitude.

In its statement Wednesday, the FAA said it was “investigating Boeing’s manufacturing practices and production lines, including those involving subcontractor Spirit AeroSystems,” which produces the 737 Max fuselage.

Boeing has said it would cooperate with the FAA investigation and announced Monday that it would make changes to its quality control processes. The planemaker declined to comment on the FAA’s statement.

A Spirit AeroSystems spokesman, Joe Buccino, said the company was “supporting Boeing’s efforts with the FAA and affected airlines as they inspect the 737-9 fleet and work to safely return those aircraft to service.”