WHIDBEY ISLAND, Wash. – Federal regulators have ordered seaplanes, like the one that went down in Mutiny Bay in September, be inspected for a flaw that likely caused the deadly crash.

The FAA airworthiness directive requires that operators of all the DHC-3 Otter seaplanes in the US examine the stabilizer to confirm the condition of an actuator piece.

That piece was missing from the Friday Harbor Seaplanes aircraft that crashed Sept. 4 into the waters near Whidbey Island, killing 10 people.

Operators must confirm that the stabilizer actuator lock ring is correctly installed and report back to the FAA by Dec. 19, according to the directive.

On Oct. 24, the National Transportation Safety Board urged operators to ground those particular planes until the part is inspected.

It took the NTSB and U.S. Navy crews more than a week and several types of sonar to find what remained of the plane because of the depth and current of the channel where the aircraft hit.