Boeing Says Software Fix to Always Allow Override of Anti-Stall System

Boeing said on Thursday that a new software fix for its anti-stall system, at the centre of investigations into two deadly plane crashes, will give pilots the authority to always override the system if activated by faulty sensor data.

The world's largest planemaker, facing its worst crisis in years and the worldwide grounding of its top-selling jetliner, said its software upgrade and associated pilot training will add additional layers of protection to prevent erroneous data from triggering its so-called MCAS system.

The system activated in the Ethiopian Airlines crash last month and also during a separate Lion Air crash in Indonesia in October, Boeing said in a statement following the release of preliminary findings from Ethiopia.

"Understanding the circumstances that contributed to the Ethiopian accident is critical to ensuring safe flight," Boeing Commercial Airplanes Chief Executive Kevin McAllister said in a statement.

He said Boeing would carefully review the preliminary report and take "any and all" additional steps necessary to enhance the safety of Boeing aircraft.

Ethiopian Airlines' doomed 737 Max jet hit excessive speed and was forced downwards by a wrongly-triggered automation system as pilots wrestled to regain control, a separate preliminary report into the crash that has shaken the aviation world showed on Thursday.

According to the preliminary report, an alarm indicating excess speed was heard on the cockpit voice reporter as the jet reached 500 knots (575 miles per hour) - well above operational limits.

The plane had faulty "angle of attack" sensor readings, its nose was pushed down automatically, and the crew lost control despite following recommended instructions, it said.

Three times the captain, Yared Getachew, cried "pull up", before the Boeing plane plunged into a field six minutes after takeoff from Addis Ababa, killing all 157 passengers and crew, said the report by Ethiopian investigators.

The March 10 disaster, and parallels with another 737 Max crash in Indonesia last October in which 189 people died, has led to the worldwide grounding of Boeing's flagship model.

It has also brought uncomfortable scrutiny over new software, pilot training and regulatory rigour.