The cockpit voice recorder from the Boeing 737 MAX 9 jet that suffered a plug door blowout during an Alaska Airlines flight and carried out an emergency landing on Friday was overwritten by the time it was recovered, the National Transportation Safety Board chair said Sunday.

NTSB chair Jennifer Homendy said the flight data recorder and cockpit voice recorder were sent to NTSB labs on Sunday to be read, but no data was available on the cockpit voice recorder because it was not retrieved by the two-hour mark, when recording restarts and previous data is erase.

"It's a very chaotic event. The circuit breaker for the CVR (voice recorder) was not pulled. The maintenance team went out to get it, but it was right at about the two-hour mark," Homendy said.

The NTSB has pushed to extend the cockpit voice-recording requirement to 25 hours. The Federal Aviation Administration issued a proposed rule in November that would increase the requirement, but it would only apply to newly manufactured aircraft, Homendy said.

"If that communication is not recorded, that is unfortunately a loss for us and a loss for the FAA and a loss for safety because that information is key not just for our investigation but for improving aviation safety," she said.