Both the Ethiopian Airlines and the Lion Air pilots reported similar "flight-control problems" to air traffic control shortly after take-off, adding to suspicions that the problem is intrinsic to the aircraft.
Here's what we know about the Ethiopian Airlines crash so far.
At the rural site where Flight ET 302, which was bound for the Kenyan capital Nairobi, came down near the village of Gora-Bokka, dozens of grief-stricken relatives paid their respects.
The cause of the disaster is not yet clear.
A resident who is flying with Sunwing from Waterloo next week says his flight confirmation had information about the model of plane he'll be on.
The flight data and cockpit voice recorders from Flight 302 have been recovered, the airline announced on Monday.
The question then arises: if this latest crash is proven to have been caused by the aircraft's systems doing just that, did the pilots apply the checklist procedure?
It's unclear whether the two plane tilting reports led to any actions by the FAA or the pilots' airlines.
But he said he was thankful the FAA chose to ground the Max 8 jets while the investigation continues.
The MCAS, which stands for Manoeuvring Characteristics Augmentation System, is created to prevent the plane stalling when making steep turns under manual control.
As a flight leaves the runway and climbs, "angle-of-attack sensors" measure how steeply the plane is ascending; if the angle is too abrupt, the engines can stall.
"You can flex up in utilization in the aircraft", Mann said. Thailand ordered budget airline Thai Lion Air to suspend flying the planes for risk assessments.
"We are making adjustments to our schedule to minimize the disruption to customers as much as possible by optimizing the deployment of the rest of our fleet and looking at alternative options, including accommodating customers on other airlines", said Air Canada spokesperson Isabelle Arthur in an emailed statement.
The United States had held back on suspending 737 MAX flights on Tuesday even as numerous world's top economies such as China and European nations grounded the plane.
President Trump had a phone call with Boeing chief executive Dennis Muilenburg on Tuesday but has not made a final decision on what should be done in response to the crashes, according to a senior administration official. They have been in commercial use since 2017. He acknowledged Southwest might have trouble with operational reliability until its Max jets can fly again, but said it probably won't be material to its financial results.
"We respect the decision made by Transport Canada and are in the process of grounding the 13 Max aircraft in our fleet", WestJet said in a news release posted to its website.
The last fleet-wide grounding by the FAA occurred on January 17, 2013, when it ordered a halt to revenue flights by Boeing's then-new model, the mostly composite 787, after a lithium-ion batteries on the plane overheated.
FILE PHOTO: A Boeing 737 MAX 8 aircraft is parked at a Boeing production facility in Renton, Washington, U.S., March 11, 2019.
The grounding applies to 737 Max aircraft operated by US carriers or in USA territory and will remain in effect pending further investigation, the agency said in a statement Wednesday.