No passengers were on board.
The March 13 order to ground the planes, which came after other airlines and countries around the world had already done so, was based on enhanced satellite data Elwell said he received that morning.
Below are the changes it is making: The Maneuvering Characteristics Augmentation System (MCAS) flight control software was installed on the 737 MAX because the heavier engines forced a shift in the placement of the engines.
The Southwest crew declared an emergency after taking off from Orlando at about 2.50pm on Tuesday.
In Seattle, Boeing said the process by which it designs, develops and tests planes has led to safer air travel, and it sees no need for an overhaul.
Embattled aviation giant Boeing pledged Wednesday to do all it can to prevent crashes like two that killed almost 350 people in recent months, as it unveiled a fix to the flight software of its grounded 737 MAX aircraft. In October of a year ago, Lion Air flight 610 crashed off the coast of Indonesia 13 minutes into its flight, killing all 189 on board.
The data Elwell said he received showed similarities between the March 10 crash of Ethiopian Airlines flight 302, which killed 157 people, and the October 29, 2018, crash of Lion Air flight 610 in Indonesia, which killed 189.
To avert this outcome and save the lives of the 189 people on board, pilots would have had to completely shut off the power from the anti-stalling system, but that would require knowledge about two more switches that apparently the pilots didn't have. "Contrary to some media reports, our pilots who fly the new model were trained on all appropriate simulators", he stated.
The update will compare readings from two angle-of-attack sensors, which measure the angle of a plane's nose against onrushing wind.
This must all be done extremely quickly otherwise attempts to resolve the problem might be too late. Pilots will gain more training via a tablet, including a test.
There would still be scarcely enough time to diagnose and solve the problem.
Reuters reported in November after the Lion Air disaster that some aviation experts believed the optional alert could have alerted engineers about mechanical faults, leading to an industry debate over whether the system should be mandatory.
They also questioned whether a 56-minute iPad course on the MAX had been sufficient.
Boeing also will install a warning feature-at no cost-called a "disagree light" to indicate to the pilot when the left and right AOA sensors are out of sync. The earlier software only included data from one of such sensor. The flight-crew operations manual will describe the speed trim system that has been used on the 737 Next Generation family along with MCAS. That system is suspected in both crashes because flight paths show the planes repeatedly climbing and diving.
The software update will affect software known as the Manoeuvring Characteristics Augmentation System (MCAS), which is created to automatically command a plane down if it senses an imminent stall.
Any fixes to the MAX software must still get approval from governments around the world. Within less than a week after the Ethiopian crash, the jets were grounded globally. Currently, Lufthansa does not have any Boeing 737 MAX aircraft in its fleet, so the recent grounding has not made an impact on its revenue or flight service.