Enlarge / The 737 MAX cockpit’s layout is practically identical to this 737-800’s. The software program behind the glass is not.

Delivery of Boeing’s promised repair to the flight method software at the center of two 737 MAX crash investigations has been pushed back various weeks right after an internal overview by engineers not connected to the aircraft raised further security concerns. The benefits of the “non-advocate” overview have not been revealed, but the Federal Aviation Administration confirmed on April 1 that the software program required further function.

“The FAA expects to get Boeing’s final package of its software program enhancement more than the coming weeks for FAA approval,” an FAA spokesperson stated in a statement. “Time is required for further function by Boeing as the outcome of an ongoing overview of the 737 MAX Flight Handle Program to guarantee that Boeing has identified and appropriately addressed all pertinent difficulties.”

The Maneuvering Traits Augmentation Program (MCAS) was created by Boeing to mitigate adjustments in the handling of the 737 MAX from other 737 styles. It integrated a far more aggressive anti-stall function intended to counter the modified aircraft’s inherent tendency to “nose up” for the duration of flight—automatically correcting the position of the aircraft’s stabilizers to bring the nose back down. Proof from the crashes of a Lion Air 737 MAX off Indonesia in October and an Ethiopian Airlines flight final month indicates that a single faulty sensor input brought on the anti-stall method to activate in error, pushing each aircraft into a dive shortly right after take-off. Lack of diagnostic info and a modify in how pilots would typically disable the software program also contributed to the Lion Air crash the investigation of the Ethiopian Airlines crash is nonetheless in progress.

Boeing had previously detailed its plans for adjustments in the MCAS, which the enterprise began function on following the Lion Air crash in October. The updated software program will use sensor inputs from each of the aircraft’s “angle of attack” (AOA) sensors on the aircraft’s nose rather than relying on a single sensor. An AOA sensor “disagree” indicator on the aircraft’s cockpit show, previously an optional element of MCAS, will be created regular for all 737 MAX aircraft. And the update will make MCAS much less aggressive in its level of manage more than the aircraft’s stabilizers. These adjustments may have further effect on the all round handling of the 737 MAX and will probably demand further pilot education as portion of any rollout.

It is not clear how considerably priority Boeing had placed on improvement of the MCAS patch prior to final month’s Ethiopian Airlines crash. In March, the Wall Street Journal reported that unnamed FAA officials had stated the pace of the improvement of the software program patch had been impacted by the government shutdown in December and January. Though Boeing’s personal workers are involved in security certification function, they do that function below the auspices of the FAA.

Just how far back the delivery of the MCAS patch has been pushed is uncertain. The New York Instances reports that the update’s schedule has been pushed back “several weeks.” And right after its delivery, an FAA spokesperson stated, “the FAA will topic Boeing’s completed submission to a rigorous security overview. The FAA will not approve the software program for installation till the agency is happy with the submission.”

This signifies it could be months prior to grounded Boeing 737 MAX aircraft are after once again deemed airworthy. And that signifies far more flight cancellations for airlines that have the aircraft in their inventory. Southwest Airlines, Boeing’s biggest 737 MAX client, canceled all of its flights dependent on its 34 737 MAX aircraft by means of April 20 so far—about 150 flights per day. And Boeing’s delivery of new 737 MAX aircraft—the company’s greatest-seller—has been indefinitely delayed.