The five-week government shutdown delayed an important software fix to the Boeing 737 Max 8, The Wall Street Journal reported Tuesday.

The shutdown delayed a software update once expected as early as January by five additional weeks, The Journal said, citing US officials.

April is the new expected date for the fix, according to Boeing, whose planes are under scrutiny after a 737 Max 8 on Sunday crashed for the second time in five months.

After one of its 737 Max 8 planes crashed in October, Boeing was working on a software update for a safety feature designed to pitch the plane's nose down to avoid a stall.

On Monday, the day after a second 737 Max 8 plane crashed, the company said it had been working on an enhancement for its flight-control software "for the past several months."

That effort was complicated, however, by the 35-day government shutdown that ended in February, The Wall Street Journal reported Tuesday.

With all but the most essential government staff and contractors — air-traffic controllers and safety oversight workers, for example — on furlough, the software fix that was originally expected to be delivered as early as January was delayed a further five weeks, The Journal said, citing US officials.

The regulatory Federal Aviation Administration approved the delay because Boeing and other experts saw no immediate safety threat, a source told The Journal.

Acting FAA administrator Daniel Elwell told reporters in Washington D.C. on Wednesday that the government shutdown had no effect on the software update.

That view has come under scrutiny since Sunday, when Ethiopian Airlines Flight 302 crashed shortly after takeoff, killing all 157 on board. As the second crash of a 737 Max 8 in less than five months, it has prompted most of the world's countries — but not the US — to bar the plane from traveling to their airports or even in their airspace.

Read more: Everything we know about Ethiopian Airlines' deadly crash of a Boeing 737 Max 8, the 2nd disaster involving the plane in 5 months

Lawmakers have called on the FAA to follow suit, but as of Tuesday the agency was standing by its decision to continue to allow the plane to fly. The US-based carriers that operate the plane, Southwest, American, and United, were also standing by their fleet.

"The FAA says it anticipates mandating this software enhancement with an Airworthiness Directive (AD) no later than April," Boeing said. "We have worked with the FAA in development of this software enhancement."

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