US regulators said Monday they ordered inspections of pilot seats on hundreds of Boeing 787 planes following a March flight in which the plane's sudden plunge led to passenger injuries.

The Federal Aviation Administration is requiring inspections after a report "of uncommanded movement of the captain's seat in the forward direction that caused a rapid descent," the agency said in a statement.

Operators are also required to perform necessary corrective actions under the airworthiness directive, which affects 158 US-registered 787 Dreamliner models and 737 planes worldwide, the FAA said.

The move is in response to a March flight on a New Zealand-bound plane operated by LATAM Airlines that suddenly lurched downward while flying from Sydney to Auckland, injuring some 50 passengers.

Since that incident, the FAA has received reports from Boeing of four additional instances of "uncommanded horizontal movement" of the captain and first officer's seats, the agency said.

Three of the incidents were due to "loose" switch caps on the seat, while the other two incidents are under investigation, the FAA said.

The "unintended and sustained movement of the seat" can lead to "in-flight upset from unintended and abrupt flight control inputs, which could result in a rapid descent of the airplane and serious injury to passengers and crew," the FAA said.

"The FAA is issuing this airworthiness directive to address the unsafe condition on these products," the agency added.

Boeing did not immediately respond to a request for comment.