WRAPUP 3-World wants answers from Indonesia and Ethiopia crashes

* Lion Air crash investigator describes panic in final seconds

* Ethiopian crash pilot untrained on 737 MAX simulator - source

* Flight control system MCAS at centre of investigations

* Training required after Boeing software update - union

* Ralph Nader joins campaign for answers

JAKARTA/WASHINGTON, March 21 (Reuters) - Indonesian investigators described the panic of pilots grappling with airspeed and altitude problems in the last moments of their doomed Lion Air flight, as comparisons mounted to a disaster in Ethiopia and authorities queued up to question Boeing.

The March 10 Ethiopian Airlines crash that killed all 157 on board has set off one of the widest inquiries in aviation history and cast a shadow over the Boeing 737 MAX model intended to be a standard for decades.

Initial investigations show similarities between the Ethiopian crash and the Indonesian accident in October that killed all 189 crew and passengers.

"At the end of the flight it seemed the pilot felt he could no longer recover the flight. Then the panic emerged," Nurcahyo Utomo, an investigator at Indonesia's national transportation committee, told reporters in Jakarta on Thursday.

Reuters reported on Wednesday that the Lion Air pilots scrambled through a handbook to understand why the jet was lurching downwards in the final minutes before it hit the water.

A final report on the Lion Air crash, which has taken on new urgency since the Ethiopian one, is expected in August.

Boeing, fighting to retain its prestige as the world's biggest planemaker and one of the United States' most important exporters, has said there was a documented procedure to handle the automated system at the heart of the problem.

In both flights, crews radioed about control problems shortly after take-off and sought to turn back.

MULTIPLE INQUIRIES

Investigations of the planemaker's conduct are starting to pile up, with several lawsuits already filed on behalf of victims of the Lion Air crash referring to the Ethiopian accident. Boeing said it did not respond to, or comment on, questions concerning legal matters.

Veteran consumer advocate and former U.S. presidential candidate Ralph Nader lost a grand-niece in the Ethiopian crash and urged whistleblowers to help challenge the aviation industry and get to the bottom of what happened.

"They lulled us into complacency," he said in an interview in Thursday's Wall Street Journal, urging grassroots pressure both on Boeing and the U.S. Federal Aviation Authority (FAA).

The first report from Ethiopia's inquiry is expected within a month. While no direct link has been proven between the two crashes, investigators are focussing on an automated flight-control system, MCAS (Maneuvering Characteristics Augmentation System), that came into service with the MAX two years ago.

The software is designed to prevent a loss of lift which can cause an aerodynamic stall, sending the plane downwards in an uncontrolled way. In the Lion Air crash, it may have been erroneously activated by a faulty sensor, investigators believe.

Boeing will mandate a previously optional cockpit warning light as part of its forthcoming update to software in its MAX fleet, two officials briefed on the matter said.

The FAA has said installation of the new software and related training was a priority.

For now, more than 350 MAX aircraft are grounded, and deliveries of dozens of planes out of an order backlog of nearly 5,000, worth more than $500 billion at list prices, are on hold.

Boeing's shares have fallen 11 percent since the Ethiopian Airlines crash, wiping $26 billion from its market value.

The first major pilots' union to comment - that of Southwest Airlines, which has the world's biggest 737 MAX fleet - said on Wednesday extra computer-based training would be required after the software update.

SIMULATORS

A Boeing spokeswoman said training on the software update would be provided by the manufacturer, but declined to disclose further details.

Simulators for the Boeing 737 MAX are now being manufactured but they have yet to be delivered to most airlines that have ordered them. They have not formed part of the required conversion training for existing 737 pilots and are not designed to replicate the MCAS system problems, Ethiopian Airlines said.

It is among the few that do have such a simulator but the captain of the doomed flight had no chance to practise on it before the fatal crash, a pilot colleague said.

In Washington D.C., Boeing is facing various investigations.

The Federal Bureau of Investigation has joined a criminal probe into the certification of the 737 MAX, the Seattle Times reported, while the Pentagon Inspector General will investigate whether acting Secretary of Defense Patrick Shanahan, a former Boeing executive, violated ethical rules by allegedly promoting the company when in office.

Boeing will also be summoned to a U.S. Senate panel hearing for questioning over the crashes, and the panel will separately question FAA officials.

Regulators in Europe and Canada have said they will seek their own guarantees of the MAX's safety.

(Additional reporting by Jamie Freed in Singapore, Bernadette Christina Munthe in Jakarta, Maggie Fick and Jason Neely in Addis Ababa, Tim Hepher in Paris, Tracy Rucinski in Chicago; Writing by Sayantani Ghosh and Georgina Prodhan; Editing by Clarence Fernandez and Andrew Cawthorne)