CHICAGO/SINGAPORE • Pressure is mounting on Boeing in Washington, with US lawmakers calling for executives to testify about two crashed 737 Max jets even as the world's biggest plane-maker worked to return the grounded fleet to the skies.
A Senate panel plans to schedule a hearing with Boeing at an unspecified date, officials said, the first time a US congressional committee has called the company's executives to appear for questioning over the crashes.
The same panel, the Senate Commerce sub-committee on aviation and space, will also question Federal Aviation Administration (FAA) officials on March 27, likely about why the regulator agreed to certify the Max planes in March 2017 without requiring extensive additional training.
The Ethiopian Airlines crash on March 10 that killed all 157 on board has set off one of the widest investigations in aviation history.
Initial reports by investigators say there are clear similarities between the crash and the Lion Air accident that killed all 189 crew members and passengers in October.
While no direct link has been established, the flight control software and related pilot training are at the centre of the investigation. US lawmakers are questioning the FAA's certification of Max's safety.
Boeing has promised a swift update to the flight control system - dubbed the Manoeuvring Characteristics Augmentation System - and the FAA said the installation of new software and related training was a priority.
However, extra computer-based training will be required after the software update, the pilots' union of Max's biggest customer, Southwest Airlines, said on Wednesday. It is the first major airline union to comment.
Southwest Airlines Pilots' Association said it had previewed the proposed Boeing training, including a required test, which would be mandatory for Southwest pilots before flying the 737 Max again.
A Boeing spokesman said training on the software update would be provided by the manufacturer, but declined to give further details.
The Seattle Times reported the Federal Bureau of Investigation (FBI) was joining the investigation into the Max's certification. An FBI spokesman in Seattle would neither confirm nor deny that it was a part of any investigation.
Criminal prosecutors at the US Justice Department, who are also investigating the FAA's oversight of Boeing, have issued multiple subpoenas to Boeing, CNN reported, citing sources briefed on the matter.
Meanwhile, the Pentagon Inspector-General said it would investigate a complaint that Acting US Secretary of Defence Patrick Shanahan, a former Boeing executive, violated ethical rules by allegedly promoting Boeing while in office.
The Ethiopian Airlines crash has shaken the global aviation industry and cast a shadow over the Boeing model intended to be a standard for decades to come.
Boeing was sued on Wednesday in federal court in Chicago by the estate of one of the Lion Air crash victims, in which the plaintiffs referred to the Ethiopian crash to support a wrongful death claim against the company.
Separately, Ethiopia's civil aviation head Wosenyeleh Hunegnaw said he expected a report on the crash investigation within 30 days.
For now, more than 350 Max aircraft are grounded and deliveries of nearly 5,000, worth more than US$500 billion (S$674 billion), are on hold.
Boeing's shares have fallen 11 per cent since the Ethiopian Airlines crash, erasing US$26 billion from its market value.