The losses, if they hold through normal trading hours, would set the stock for its biggest fall in nearly two decades, halting a surge that has seen it triple in value in just over three years to a record high of $446 last week.
A Nairobi-bound Boeing 737 MAX 8, operated by Ethiopian Airlines, crashed minutes after take-off from Addis Ababa on Sunday, killing all 157 on board.
The same model, flown by Lion Air, crashed off the coast of Indonesia in October, killing all 189 on board.
Search for clues to Ethiopia crash as China grounds Boeing 737 MAX 8
Boeing said on Monday the investigation into the Ethiopian Airlines crash is in its early stages and there is no need to issue new guidance to operators of its 737 MAX 8 aircraft based on the information it has so far.
"We anticipate heightened volatility in Boeing shares," Morgan Stanley analyst Rajeev Lalwani said. "Though it is early to draw conclusions, there may be concerns of disruption around safety, production, groundings, and/or costs, all of which should be manageable longer-term."
He said he was not changing the bank's positive "overweight" recommendation on Boeing shares for its customers, and that any corrective action the company has to take on its best-selling passenger plane will likely prove a longer-term buying opportunity.
Wall Street has been overwhelmingly bullish on Boeing - 19 of the 24 brokerages covering the stock rate it "buy" or higher, while five have a "hold" rating.
Boeing has been the best performer in the Dow Jones Industrial Average Index so far this year, rising 31% compared with a 9.1% gain in the index.
China, Indonesia ground Boeing 737 MAX 8 fleets after Ethiopia crash
The decline on Monday was a major factor in pulling Dow futures lower. Investigators have found the black box from the fatal crash with both the cockpit voice recorder and digital flight data, Ethiopian state TV reported on Monday, which should shed light on the cause of the crash.
Earlier in the day, China's aviation regulator grounded nearly 100 Boeing 737 MAX 8 aircraft operated by its airlines after the crash.
Boeing's shares lost 12% in the weeks following the Lion Air crash last year, but have more than recouped those declines. They were down 11.38% at $374.17 in pre-market trading.
Dallas-based Southwest Airlines Co - the biggest operator of MAX 8 - fell 2% to $50.75 in pre-market trade, while American Airlines Group Inc, which has 24 MAX 8 jets, was down 1.1% at $31.55.
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