The Boeing 737 MAX is the latest generation of Boeing's best selling narrow body aircraft , the 737. It was made to be more efficient than the older Boeing 737 generations. It featured a much more efficient engine named the CFM Leap 1B by providing higher bypass ratio than the older CFM56 7B engines fitted on the 737 NGs. It also featured a new split scimitar winglet design which was proved to provide more efficiency than the older blended winglets. Due to the higher bypass ratio the CFM Leap 1B engines are much bigger than the CFM56 7B engines and couldn't fit under the wing of the aircraft. Therefore it had to be raised and moved a bit forward to get a good enough ground clearance.Due to this the aircraft had a tendency to pitch up more during take off.This was the main reason  for developing a system called MCAS (Maneuvering Characteristics Augmentation System).The function of MCAS was to provide a correction to this excessive pitch up movement by trimming the aircraft down to the required pitch attitude.This function was however not mentioned to the pilots.The MAX showed a great success from the beginning till the point where there was a crash involved with the MAX.The first crash occurred on Oct 29 2018 when the aircraft was just few months from introduction.The incident involved a Lion Air Boeing 737 MAX  which dove into the Java Sea just 13 minutes after takeoff from Jakarta in Indonesia.189 people where killed in the incident. The second crash occurred on March 10 2019 where an Ethiopian Airlines Boeing 737 MAX flying from Addis Ababa International Airport heading to Nairobi, Kenya crashed 40 miles from the airport again after a dive.The pilots of the aircraft declared a Mayday and was turning back to the same runway that they have departed from but unfortunately they couldn't make it.149 passengers and eight crew members where killed int this incident.The aircraft involved was just 4 months old.Both the crashes led to the malfunction of MCAS.The MCAS system was mainly depending on the Angle of attack sensor from the captain side(left side) of the aircraft.After the incidents several countries started grounding the MAXs after the concern of safety of these aircrafts.Therfore Boeing had no other choice other than fixing the problem.The engineers at boeing came up with an idea of combining the information from both the angle of attack sensors and a way to deactivate MCAS in these kind of situations.Now after 2 years of grounding the aircraft returned to service.Still we have some countries that haven't given approval to airlines to fly their 737MAXs in their airspace or to airports in that country.Considering the modifications done we can trust  the MAX and can consider it for flying