Everything you need to know about the Boeing 737 MAX crashes

Following 2 similar crashes of Boeing 737 MAX 8 planes that killed a total of 346 people, the aircraft have been grounded worldwide as a series of investigations look into what caused the crashes and any potential flaws that went unnoticed during the safety certification process.

Context: The FAA's approval process was designed to be seamless in that airlines that already flew other versions of the best-selling 737 series were able to treat the MAX as another in the series. This limited the training requirements for 737 MAX pilots and kept customer costs down. However, in reality, the plane had many new pieces of hardware, including more powerful engines, a redesigned tail, new wing design and, crucially, new software.

Key players

• Federal Aviation Administration: Responsible for certifying new planes and has faced criticism for not grounding the Boeing 737 MAX jets faster. The organization is also also under scrutiny for delegating certification activities to Boeing.
• Boeing: Manufactures the 737 MAX series and is currently being investigated by the House, Senate, Transportation Department's Inspector General, Justice Department and FBI on how the 737 MAX was certified as safe to fly in 2017 and judged safe enough to continue to fly after October's Lion Air crash in Indonesia.
• The plane has racked up more than 5,000 orders to become the best-selling aircraft in Boeing history.
• American Airlines, Southwest Airlines and United Airlines: U.S. airlines that fly the 737 MAX.
• Airbus: Boeing's archrival in the aircraft business, which makes the Airbus A320neo, the competitor to the 737 MAX. News reports have indicated that the FAA and Boeing employees felt pressured to quickly approve the 737 MAX to keep pace with Airbus' development.

Key terms

• Maneuvering Characteristics Augmentation System (MCAS): An automated system Boeing installed to prevent the aircraft from stalling (losing lift) by pushing the plane's nose down. A malfunction with this system, where it appeared to activate based on faulty readings from a flight sensor, is the suspected cause of both crashes.

• According to the New York Times, many 737 pilots were not required to undergo intensive training in flight simulators — instead doing so on iPads. Until the Lion Air crash, many 737 MAX pilots were unaware the MCAS system existed.

Key events

• March 8, 2017: The FAA certifies the Boeing 737 MAX series.
• Oct. 29, 2018: A Lion Air Boeing 737 MAX 8 crashes into the Java Sea shortly after taking off from an airport in Jakarta, Indonesia, killing all 189 people on board.
• March 10, 2019: An Ethiopian Air flight crashes shortly after takeoff on its way from Addis Ababa to Nairobi, Kenya, killing all 157 people on board. The circumstances of this crash were similar to Lion Air.
• March 12: A number of countries around the world close their airspace to the Boeing 737 MAX planes, with Canada and the U.S. remaining key holdouts. A number of airlines also ground the plane. Meanwhile, the FAA releases a statement repeating its position that the plane is safe to fly.
• U.S. records indicate that pilots had filed at least 5 different complaints in recent months, reporting trouble retaining control of the jets while in flight. A report from the Dallas Morning News adds that one captain called the aircraft's flight manual "inadequate and almost criminally insufficient."
• March 13: Following analysis of new Ethiopian Air crash data, the FAA issues an emergency order, temporarily banning the aircraft from flying in the U.S. or entering its airspace, citing "new evidence" from the Ethiopian Airlines crash.
• Boeing also releases a statement saying it remains confident in the aircraft's safety, but recommends a temporary suspension of operations of the global fleet.
• March 17: Information retrieved from the "black boxes" of the Ethiopian Airlines crash shows "clear similarities" to the October Lion Air crash.
• A Seattle Times report revealed that deadline pressure prodded the FAA and Boeing to delegate more safety decisions to Boeing engineers working on behalf of the FAA.
• March 18: A federal grand jury issues a subpoena to at least one person involved in the aircraft's development on behalf of the Justice Department.
• March 19: Transportation Secretary Elaine Chao requests the department's inspector general investigate the process the department followed to certify the Boeing 737 MAX aircraft.
• A Bloomberg report the same day reveals that, the day before the Lion Air crash, an off-duty pilot riding in the flight deck jumpseat of the same aircraft played a pivotal role in averting a similar crash.
• March 20: Sen. Ted Cruz (R-Texas) announces he will hold a Commerce subcommittee hearing to examine the government's oversight of the jet. The FBI also announces it has joined the Department of Transportation's criminal investigation into how the Boeing 737 MAX was certified.
• In particular, Cruz plans to investigate what agencies learned between the two crashes, how that played into the FAA's decision to delay grounding the plane until virtually every other affected country had done so, and how deferential the FAA was in allowing Boeing to self-certify much of the aircraft's production.
• March 22: Indonesian airline Garuda Indonesia seeks to cancel the remainder of a $4.9 billion order for 48 more Boeing 737 MAX 8 jets.

• March 27: Boeing unveils new fixes to the MCAS software system and says it plans to send the software updates and new plans for pilot training to the FAA for approval by the end of the week.
• March 29: The investigation into the Ethiopian Airlines crash reaches a preliminary conclusion that the MCAS "activated before the plane nose-dived into the ground," according to a Wall Street Journal report.
• April 1: FAA says Boeing is expected to submit its proposal for new fixes to the MCAS software system "over the coming weeks," emphasizing more time is needed "for additional work" to ensure that Boeing "has identified and appropriately addressed all pertinent issues." Upon receiving the fix, the FAA said it will "subject Boeing's completed submission to a rigorous safety review ... [and] will not approve the software for installation until the agency is satisfied with the submission."
• The statement contrasts with early assessments that a software fix would be available soon, making clear the aircraft are unlikely to be flying again anytime soon.
• April 4: Boeing says it has identified an additional software issue the FAA will require to be repaired before the planes are cleared to fly again. It characterizes the newly detected issue as "relatively minor," but the Washington Post reports the problem is still classified as "critical for safety."
• May 5: Boeing says it knew of a safety alert flaw in the cockpit of the 737 MAX months before the Lion Air crash, but didn't immediately notify regulators.
• May 9: Bloomberg interviewed a handful of former Boeing employees who described a corporate culture that prioritizes cost-cutting and profitability over reporting plane defects to upper management.
• May 14: A preliminary conclusion from an internal FAA review has "tentatively determined that senior agency officials didn't participate in or monitor crucial safety assessments" of the MCAS system, per the Wall Street Journal.
• The results of the review indicate Boeing didn't flag the MCAS as a system whose failure could cause catastrophic damage.
• July 3: Boeing announces it plans to give $100 million to the families and communities impacted by the two fatal 737 MAX crashes.

What's next: We still don't know what caused the two crashes, if the Boeing 737 MAX is safe and how the certification process may have led to a potentially flawed aircraft being released. Boeing is working on software fixes to improve the MCAS system, but it's unclear when regulators in the U.S. and abroad may clear the plane for takeoff again. Boeing is in uncharted territory when it comes to modern aviation history: Not since the De Havilland Comet in the 1950s has a brand-new aircraft suffered such a spate of fatal incidents.

Go deeper: What we've learned from the Boeing 737 MAX crashes