The Boeing 737 MAX was allowed to fly in the United States after passing the FAA’s safety review

Boeing’s 737 MAX has been allowed to fly again in the U.S., and the Federal Aviation Administration (FAA) has given the green light to resume flights of the fateful jet,media Slash Gear reported. The decision follows a 20-month safety review following two incidents involving Lion Air Flight 610 and Ethiopian Airlines Flight 302 that killed 346 people.

The Boeing 737 MAX was allowed to fly in the United States after passing the FAA's safety review

The investigation found a serious problem with Boeing’s new 737 aircraft, the Control Feature Enhancement System (MCAS), which includes the 737-8 and 737-9. The system was designed to make the aircraft more consistent in unusual flight situations, but the FAA found that in rare cases it could also overturn the pilot’s input, causing the crash.

The MAX’s engine is mounted higher and higher on the body than the earlier 737 models. Designed to improve fuel efficiency and other reasons, this also results in upward pitching: in response, Boeing installed MCAS, which automatically fine-tunes the head down whenever the 737 MAX is in a high-slope turn or a low-speed, flap-tight flight. In the process, it can help prevent the plane from slowing down. Boeing designed the system to start without notifying the pilot when the angle of attack reaches a certain threshold.

The consequences were swift, with the 737 MAX grounded around the world and several investigations into the incident. While the FAA may have canceled the suspension, that doesn’t mean the 737 MAX will take off immediately from airports across the United States. Instead, there is a new airworthy directive detailing the design changes that the FAA says all 737 MAX aircraft must make in order to be successfully grounded.

There is also a Notice of Continued Airworthy Navigation of the International Community (CANIC) and a set of MAX training requirements. The latter details the pilot training programs that any 737 MAX operator needs to complete before it can get started. The FAA will approve any such plans by American Airlines.

Fixes to the 737 MAX include redesigning the way MCAS operates, especially how it works with Angle of Attack (AOA) sensors. Previously, only data from one sensor could trigger MCAS;

Boeing said mcAS itself would now be activated only once and “will never provide more input than pilots can fight with the lever alone”. Pilots will also be able to cover it at any time, as before. Boeing says flight control computer software has been adjusted to include more cross-checking between different aircraft control computers, and lines in some places have been adjusted to increase space.

Aircraft grounded since the airworthy order was first implemented must now go through a series of necessary maintenance steps before they can fly again. Those aircraft that have not yet been delivered are subject to face-to-face review by the FAA before they can obtain an airworthy certificate.

At the same time, Boeing has established a new Product and Service Security Department, consisting of more than 50,000 engineers, focused on “unifying the safety responsibilities of the entire company.”