Concerns about the Boeing 737 Max continue to grow after an Ethiopian Airlines flight crashed just after take-off on Sunday, killing all 157 aboard Today, the European Union suspended all 737 Max flights.

The fatal Ethiopian Airlines crash, which occurred just outside the country's capital of Addis Ababa, was the second involving the 737 Max in the past year. In October, a Lion Air flight crashed after departing Jakarta, killing 189 people. The 737 Max is a newer plane, meant for shorter flights, and it has quickly become, as the NY Times reports, Boeing's "best-selling jet ever, and it is expected to be a major driver of profits in the future. Around 5,000 of the planes are on order, with a list price of $120 million for the Max 8 version."

The European Union Aviation Safety Agency called the grounding of the 737 Max planes a "precautionary measure" in order "to ensure the safety of passengers." Before the E.U.'s decision, Britain, Germany, France, China, Indonesia, Singapore, Australia, and other countries had grounded the planes.

The investigation into the Ethiopian Air crash is just beginning, but reports about the Lion Air crash say that the pilots struggled with the plane's automatic control system. From the Washington Post: "According to the investigation into that crash, pilots wrestled with the plane because a faulty sensor and automatic feature sent its nose pointing down while the pilots struggled to lift the plane up. They requested permission to return to the airport shortly before plunging into the Java Sea."

After the Lion Air Crash, some pilots questioned whether they were adequately informed of issues with the planes' systems. Boeing CEO Dennis Muilenburg also said last year, “The bottom line here is the 737 Max is safe. This airplane went through thousands of hours of tests and evaluations, certification, working with the pilots, and we’ve been very transparent on providing information and being fully cooperative on the investigative activity.”

American Airlines and Southwest Airlines, two of the "biggest customers" of the plane, are continuing to keep the planes in the air. The Federal Aviation Administration has not made any decision yet, but a growing number of lawmakers, including Senators Mitt Romney, Richard Blumenthal, and Elizabeth Warren are asking the agency to ground the planes. Senator Ted Cruz today said he would hold hearings on the matter. And a union representing flight attendants also asked for the planes to be grounded:

The NY Times notes, "Pilots in the rapidly expanding aviation markets of East Asia and in developing countries tend to be much less experienced than their counterparts in the West. Li Jian, the deputy director of China’s Civil Aviation Administration, said the agency — the first to ground the 737 Max after the accident Sunday — worried about the challenges that could face pilots if an aircraft had unexpected difficulties."

The biggest worry involves possibly inaccurate signals from key flight instruments, Mr. Li said on Monday. Many pilots with less experience depend heavily on automatic systems to help them fly planes, and such systems in turn need reliable data.

“We are facing uncertainties about whether pilots have the courage or the capability to fly” if an aircraft has difficulties, Mr. Li said.

“When a pilot is operating manually, if he receives inaccurate signals, which has happened multiple times, it will bring trouble,” Mr. Li said. “As a government supervision department, we should make sure all problem are solved before we allow aircraft to be used.”

Now, Boeing promises to make "significant" changes to its software by the end of April; the Wall Street Journal reports, "The change, which was in the works before the Ethiopian Airlines plane crash over the weekend, would mark a major shift from how Boeing originally designed a stall-prevention feature in the 737 MAX when it first delivered to airlines in 2017... A company spokesman confirmed the update would include a change to use multiple data feeds in MAX’s stall-prevention system—instead of the current reliance on a single sensor."

While some airline passengers are trying to avoid flights with 737 Max planes (FYI, the 737 Max is not the same as 737-800), others are not as worried. One passenger who landed at LaGuardia from Miami told CNN, "If today is my day to go, it's my day, and the chances would be very rare of anything happening," while another said, "I'm very matter-of-fact about things. I mean, I can't live life worried about every bad thing that happens and when will it happen to me."

Boeing issued a statement today, "Safety is Boeing’s number one priority and we have full confidence in the safety of the 737 MAX. We understand that regulatory agencies and customers have made decisions that they believe are most appropriate for their home markets. We’ll continue to engage with them to ensure they have the information needed to have confidence in operating their fleets. The United States Federal Aviation Administration is not mandating any further action at this time, and based on the information currently available, we do not have any basis to issue new guidance to operators."