The design of the maneuvering characteristics augmentation system (MCAS) in the 737 Max relied on improper assumptions about the ability of pilots to respond to multiple alerts and indications during certain emergency scenarios, the U.S. National Transportation Safety Board (NTSB) said in a report issued Thursday that included seven recommendations to the Federal Aviation Administration (FAA). The NTSB’s report stems from its ongoing support of investigations into last October’s crash of Lion Air Flight 610 into the Java Sea and the crash this past March of Ethiopian Airlines Flight 302 near Ejere, Ethiopia.

The recommendations to the FAA arise from the NTSB’s examination of safety assessments conducted as part of the original design of the MCAS. The report further notes that FAA guidance allows certification analyses to make such assumptions without providing clear direction about the consideration of multiple flight-deck alerts and indications in evaluating pilot recognition and response. The NTSB’s recommendations call for more “robust” tools and methods or validating assumptions about pilot response to airplane failures in safety assessments developed as part of the U.S. design certification process.

“We saw in these two accidents that the crews did not react in the ways Boeing and the FAA assumed they would,” said NTSB chairman Robert Sumwalt. “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 noted that the report does not analyze the actions of the pilots involved in the Lion Air and Ethiopian Airlines accidents. That analysis continues as part of the ongoing accident investigations by the Indonesian and Ethiopian authorities, with which NTSB investigators continue to assist. The Board stressed that it has full access to information from the flight recorders, consistent with what it called standards and recommended practices for its participation in foreign investigations.

In separate statements, Boeing and the FAA reacted to the NTSB report with declarations of their respective safety commitments. “Safety is a core value for everyone at Boeing and the safety of our airplanes, our customers’ passengers and crews is always our top priority,” said the company. “We value the role of the NTSB in promoting aviation safety. We are committed to working with the FAA in reviewing the NTSB recommendations.”

For its part, the FAA expressed similar sentiments. “We welcome and appreciate the NTSB’s recommendations,” it said. “The agency will carefully review these and all other recommendations as we continue our review of the proposed changes to the Boeing 737 MAX. The FAA is committed to a philosophy of continuous improvement. The lessons learned from the investigations into the tragic accidents of Lion Air Flight 610 and Ethiopian Airlines Flight 302 will be a springboard to an even greater level of safety.”