The head of Boeing is facing questions from lawmakers in Washington as pressure mounts to explain the mistakes that led to a panel breaking off one of its planes this month.

Boss Dave Calhoun told reporters ahead of the meetings that he was prepared to share "everything I can".

But he declined to comment on a report that said the part had been improperly installed at one of the firm's plants.

The anonymous account was posted online and reported by the Seattle Times.

The post, from someone claiming to work at Boeing, described the production of Boeing's 737 planes as "a rambling, shambling, disaster waiting to happen".

It said the firm's records showed that the four bolts meant to hold the door plug in place were not installed when Boeing delivered the 737 Max 9 plane to customer Alaska Airlines.

On 5 Jan, just eight weeks later, the panel blew off shortly after take-off, terrifying passengers, and forcing an emergency return to the Portland, Oregon airport.

Boeing's mid-flight blowout a big problem for company
No serious injuries were reported but lawsuits have been filed by customers since the incident, accusing the company of negligence.

The Federal Aviation Administration (FAA) has grounded 171 other 737 Max 9 planes with similar designs for inspection, forcing the cancellation of thousands of flights.

It also recently recommended airlines inspect Boeing's older 737-900ER models, which use the same door design as Max 9s, though it did not order the planes out of service.

The whistleblower account said Boeing should have halted 737 manufacturing due to an "alarming" number of issues surfacing on the planes during inspections.

In the case of this particular plane, it said Boeing and Spirit staff at a Boeing factory in Washington worked to identify and repair issues ahead of the delivery. The whistleblower says that in the course of that work, the bolts were removed.