NTSB report on Boeing Max 737 crashes urges certifiers to test for 'real-world' chaos

"Crews did not react in the ways Boeing and the FAA assumed they would."

The National Transportation Safety Board is out with new safety recommendations Thursday urging certifiers to account for "real-world" chaos that can unfold on a plane in the wake of the two deadly Boeing 737 Max crashes that left 346 people dead.

The NTSB found that the pilots were bombarded with multiple alarms and alerts in the cockpit before the planes crashed. The blaring alarms likely caused further confusion and made an already stressful situation worse, according to the NTSB.

A scenario like the one encountered by pilots in both crashes which triggered those alarms was never tested during the certification process. The government agency also said Boeing and the FAA need to consider testing every possible scenario when certifying a new plane.

“We saw in these two accidents that the crews did not react in the ways Boeing and the FAA assumed they would,” NTSB chairman Robert Sumwalt said in a statement. “Those assumptions were used in the design of the airplane and we have found a gap between the assumptions used to certify the MAX and the real-world experiences of these crews, where pilots were faced with multiple alarms and alerts at the same time."

Sumwalt added that the safety recommendation report "addresses that issue and does not analyze the actions of the pilots" involved in the accidents.

The NTSB's new safety recommendations are not binding, meaning the FAA does not have to make any changes based on the report.

The FAA responded in a statement saying safety is its first priority and it welcomed the NTSB's recommendations.

"The agency will carefully review these and all other recommendations as we continue our review of the proposed changes to the Boeing 737 MAX," according to the statement. "The FAA is committed to a philosophy of continuous improvement. The lessons learned from the investigations into the tragic accidents of Lion Air Flight 610and Ethiopian Airlines Flight 302 will be a springboard to an even greater level of safety."

In October 2018, Lion Air Flight 610 crashed in the ocean just outside of Indonesia shortly after takeoff, killing all 189 on board, including three children. Less than six months later, in March 2019, Ethiopian Airlines Flight 302 also crashed just minutes after taking off from Ethiopia's capital, killing all 157 people on board, including eight Americans.

The 737 Max jets have been grounded since March.

ABC News' Whitney Lloyd contributed to this report.