DAYTONA BEACH, Fla. – The Boeing 737 Max 8 -- the type of plane that crashed into the Java Sea in October, killing all 189 people on board, and on Sunday, in Ethiopia, killing all 157 passengers and crew -- is just one version of the popular 737 narrow-body aircraft operated around the world.
First introduced more than a half-century ago, Boeing's 737 almost immediately became a short-haul workhouse.
Boeing introduced different sizes of 737s over the years, with different fuel and distance capabilities, including the -300, -400, -500, -600, -700, -800 and -900 variants.
Less than a decade ago, Boeing introduced its "Next Generation" 737 -- the MAX variants.
Upgrades to the MAX 8 include new engines and wing tips, a modern cabin and a computerized "glass" cockpit.
Professor Anthony Brickhouse, an air safety investigator at Embry-Riddle Aeronautical University in Daytona Beach and former National Transportation Safety Board employee, said the computer system is so advanced, it will correct a stall if it senses it and override manual input from pilots, a system known as MCAS.
"If the computer senses the plane is about to stall, the computer takes over and wants to nose the aircraft over," Brickhouse said.
Investigators are looking at the automated stall-sensing system in the Lion Air Crash of a MAX 8 in October.
"It's still being investigated, but my understanding is there may have been something wrong with the angle-of-attack sensor, which is basically the nose up/nose down pitch of the aircraft," Brickhouse said. "And because there was something wrong with that system, it caused the computer system to believe the aircraft was about to stall, so the system took over and pushed the nose down. And it looks like it caught the flight crew off guard and unfortunately, they ended up crashing."
After the Lion Air crash, Boeing warned pilots and showed them how to disengage the stall-sensing system, if necessary.
"It seems to be a link, but once again, that accident from October is still being investigated," Brickhouse said. "We're only three days into the Ethiopian crash, so it's really too early to establish that link."
Southwest Airlines, based at Orlando International Airport, said it flies 34 MAX 8s.
American Airlines is the only other U.S. carrier that flies the MAX 8.
Both airlines continue to use the planes.
The Federal Aviation Administration has expressed full confidence in the MAX 8, despite calls from some lawmakers to ground the planes and the EU, UK, China, Singapore and Australia stopping service of the MAX 8.
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Some passengers at Orlando International Airport said they changed, or considered changing, their flights when they found out they were booked on a MAX 8.
Brickhouse said passengers should consider changing planes if they don't feel comfortable.
"Considering what happened in Indonesia and Ethiopia, it's too early to say whether there is a direct correlation but members of the flying public should do their homework and say, make an educated decision on whether they're comfortable flying on an aircraft that has had two accidents in six months," Brickhouse said.
Southwest Airlines said it would re-book passengers on other planes if they don't feel comfortable flying on board a MAX 8.
President Donald Trump tweeted Tuesday that airplanes are becoming too complex to fly.
"Pilots are no longer needed, but rather computer scientists from MIT," the President tweeted. "I see it all the time in many products. Always seeking to go one unnecessary step further, when often old and simpler is far better. Split second decisions are ... needed, and the complexity creates danger. All of this for great cost, yet very little gain. I don’t know about you, but I don’t want Albert Einstein to be my pilot. I want great flying professionals that are allowed to easily and quickly take control of a plane."