WASHINGTON (CNN) - US officials say the recent government shutdown played a part in the delay of Boeing's software update for its 737 Max aircraft, which has been grounded by airlines and countries after two deadly accidents in the past five months, the Wall Street Journal reported.
Boeing announced Monday it had been working on a software fix for the 737 Max aircraft over "the past several months and in the aftermath" of Lion Air Flight 610 that went down in late October over the Java Sea off Indonesia, killing 189 passengers. The process was underway before the Ethiopian Airlines Flight 302 crash over the weekend, which killed 157 people and also involved a 737 Max. Both flights crashed minutes into their journeys.
The circumstances of the crashes remain under investigation.
Boeing, which said it was working with the Federal Aviation Administration "on development, planning and certification of the software enhancement," said the fix will be on 737 Max planes no later than April.
But the company's software update had initially been expected in early January, the Journal reported.
Citing people familiar with the details, the Journal reported that discussions between the FAA and Boeing about the software fix dragged on, in part because of "differences of opinion about technical and engineering issues."
Boeing and FAA officials also couldn't agree on how extensive the software enhancement should be, the newspaper reported. US officials also said the recent government shutdown, the longest in US history, delayed work on the update for five weeks, the Journal noted.
The FAA was one of the agencies affected by the government shutdown, which began on December 22 and spanned 35 days. The agency had to recall thousands of its aviation inspectors from furlough over safety concerns.
The FAA determined that the delay in the update was acceptable because its experts and Boeing deemed there was no imminent safety threat, an unnamed source briefed on the discussions told the Journal.
Boeing declined to comment to CNN about the Wall Street Journal's reporting.
Though international airlines and foreign governments have grounded Boeing 737 Max 8 planes, the US and Boeing have not, with the company saying it has "full confidence in the safety of the MAX."
The FAA and Boeing say the software upgrade that's due in April will give pilots greater control in case problems emerge with the planes' safety systems.
Boeing said the company plans to include an update to the Maneuvering Characteristics Augmentation System (MCAS) flight control law.
"The enhanced flight control law incorporates angle of attack (AOA) inputs, limits stabilizer trim commands in response to an erroneous angle of attack reading, and provides a limit to the stabilizer command in order to retain elevator authority," Boeing said.
The software fix will also include updates to pilot displays, operation manuals and crew training.