The nearly 400 Boeing 737 Max planes in airline fleets were grounded by aviation authorities in mid-March after a second deadly crash of the fast-selling plane in less than five months. Investigators in the latest crash, in Ethiopia, have pointed to an automated anti-stall system the that pilots battled in the last minutes of both crashes.

Shares of the airplane manufacturer rose after it released its statement, trading up 2.8 percent late in the session.

Boeing said Thursday that it has completed a software update for its 737 Max planes, a key step in getting the aircraft flying again after aviation authorities grounded the jets around the world following two fatal crashes.

The system, known as MCAS, pushes the plane's nose down repeatedly if the aircraft's software senses it is going into a stall. That is a normal position to avoid a stall, but it can be catastrophic if the plane is not actually in a stall. Crash investigators have implicated the system in the Ethiopia crash and another 737 Max crash in October, saying it was triggered by bad data from the sensors.

On Thursday, Boeing said it has flown the 737 Max with the updated software for 360 hours on 207 flights. It also, as planned, has provided updating training materials for 737 Max pilots.

Some pilots complained that they were not told that the MCAS system was even on the planes, until after the October crash of Lion Air Flight 610, which killed all 189 on board. In order to transition from an older model of the Boeing 737 to the 737 Max, pilots said they were given training on a computer or tablet, with some courses that were less than an hour long. MCAS was not mentioned.

Boeing's lack of disclosure has drawn scrutiny from lawmakers as well as the pilots. FAA's acting chief, Daniel Elwell, at a House aviation panel's hearing on Wednesday said the new MCAS system should have been included in pilot manuals.

How the Boeing 737 Max won approval from the FAA is the subject of several federal investigations and others by lawmakers.

Read Boeing's full statement here:

Boeing has completed development of the updated software for the 737 MAX, along with associated simulator testing and the company's engineering test flight. To date, Boeing has flown the 737 MAX with updated MCAS software for more than 360 hours on 207 flights. Boeing is now providing additional information to address Federal Aviation Administration (FAA) requests that include detail on how pilots interact with the airplane controls and displays in different flight scenarios. Once the requests are addressed, Boeing will work with the FAA to schedule its certification test flight and submit final certification documentation. "With safety as our clear priority, we have completed all of the engineering test flights for the software update and are preparing for the final certification flight," said Boeing Chairman, President and Chief Executive Officer Dennis Muilenburg. "We're committed to providing the FAA and global regulators all the information they need, and to getting it right. We're making clear and steady progress and are confident that the 737 MAX with updated MCAS software will be one of the safest airplanes ever to fly. The accidents have only intensified our commitment to our values, including safety, quality and integrity, because we know lives depend on what we do." In addition, Boeing has developed enhanced training and education materials that are now being reviewed with the FAA, global regulators, and airline customers to support return-to-service and longer-term operations. This includes a series of regional customer conferences being conducted around the world.

Correction: This story has been updated to note that Boeing conducted 207 test flights, not 270.

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