SEATTLE, WA - JUNE 27: Boeing 737 MAX airplanes are stored on employee parking lots near Boeing Field, on June 27, 2019 in Seattle, Washington. After a pair of crashes, the 737 MAX has been grounded by the FAA and other aviation agencies since March, 13, 2019. The FAA has reportedly found a new potential flaw in the Boeing 737 Max software update that was designed to improve safety. (Photo by Stephen Brashear/Getty Images)
Stephen Brashear/Getty Images North America/Getty Images
SEATTLE, WA - JUNE 27: Boeing 737 MAX airplanes are stored on employee parking lots near Boeing Field, on June 27, 2019 in Seattle, Washington. After a pair of crashes, the 737 MAX has been grounded by the FAA and other aviation agencies since March, 13, 2019. The FAA has reportedly found a new potential flaw in the Boeing 737 Max software update that was designed to improve safety. (Photo by Stephen Brashear/Getty Images)
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A Boeing 777X model is displayed at the Airshow China 2018 in Zhuhai in southern China's Guangdong province on November 7, 2018. (Photo by WANG Zhao / AFP)        (Photo credit should read WANG ZHAO/AFP/Getty Images)
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VICTORVILLE, CA - MARCH 27:  A number of Southwest Airlines Boeing 737 MAX aircraft are parked at Southern California Logistics Airport on March 27, 2019 in Victorville, California. Southwest Airlines is waiting out a global grounding of MAX 8 and MAX 9 aircraft at the airport.  (Photo by Mario Tama/Getty Images)
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VICTORVILLE, CA - MARCH 27: A number of Southwest Airlines Boeing 737 MAX aircraft are parked at Southern California Logistics Airport on March 27, 2019 in Victorville, California. Southwest Airlines is waiting out a global grounding of MAX 8 and MAX 9 aircraft at the airport. (Photo by Mario Tama/Getty Images)
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RENTON, WA - MARCH 11: The Boeing 737-8 is pictured on a mural on the side of the Boeing Renton Factory on March 11, 2019 in Renton, Washington. Two of the aerospace company's newest model airliners have crashed in less than six months. (Photo by Stephen Brashear/Getty Images)
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RENTON, WA - MARCH 11: The Boeing 737-8 is pictured on a mural on the side of the Boeing Renton Factory on March 11, 2019 in Renton, Washington. Two of the aerospace company's newest model airliners have crashed in less than six months. (Photo by Stephen Brashear/Getty Images)
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People stand near collected debris at the crash site of Ethiopia Airlines near Bishoftu, a town some 60 kilometres southeast of Addis Ababa, Ethiopia, on March 11, 2019. - An Ethiopian Airlines Boeing 737 crashed on March 10 morning en route from Addis Ababa to Nairobi with 149 passengers and eight crew believed to be on board, Ethiopian Airlines said. (Photo by Michael TEWELDE / AFP)        (Photo credit should read MICHAEL TEWELDE/AFP/Getty Images)
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People stand near collected debris at the crash site of Ethiopia Airlines near Bishoftu, a town some 60 kilometres southeast of Addis Ababa, Ethiopia, on March 11, 2019. - An Ethiopian Airlines Boeing 737 crashed on March 10 morning en route from Addis Ababa to Nairobi with 149 passengers and eight crew believed to be on board, Ethiopian Airlines said. (Photo by Michael TEWELDE / AFP) (Photo credit should read MICHAEL TEWELDE/AFP/Getty Images)
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People walk past a part of the wreckage at the scene of the Ethiopian Airlines Flight ET 302 plane crash, near the town of Bishoftu, southeast of Addis Ababa, Ethiopia March 10, 2019. REUTERS/Tiksa Negeri
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People walk past a part of the wreckage at the scene of the Ethiopian Airlines Flight ET 302 plane crash, near the town of Bishoftu, southeast of Addis Ababa, Ethiopia March 10, 2019. REUTERS/Tiksa Negeri
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RENTON, WA - MARCH 14: Boeing 737 MAX airplanes, including the 737 MAX 9 test plane (L), are seen at Renton Municipal Airport, on March 14, 2019 in Renton, Washington. The 737 MAX, Boeing's newest model, has been been grounded by aviation authorities throughout the world after the crash of an Ethiopian Airlines 737 MAX 8 on March 10.  (Photo by Stephen Brashear/Getty Images)
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RENTON, WA - MARCH 14: Boeing 737 MAX airplanes, including the 737 MAX 9 test plane (L), are seen at Renton Municipal Airport, on March 14, 2019 in Renton, Washington. The 737 MAX, Boeing's newest model, has been been grounded by aviation authorities throughout the world after the crash of an Ethiopian Airlines 737 MAX 8 on March 10. (Photo by Stephen Brashear/Getty Images)
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A grounded Lion Air Boeing Co. 737 Max 8 aircraft sits on the tarmac at terminal 1 of Soekarno-Hatta International Airport in Cenkareng, Indonesia, on Tuesday, March 15, 2019. Sundays loss of an Ethiopian Airlines Boeing 737, in which 157 people died, bore similarities to the Oct. 29 crash of another Boeing 737 Max plane, operated by Indonesias Lion Air, stoking concern that a feature meant to make the upgraded Max safer than earlier planes has actually made it harder to fly. Photographer: Dimas Ardian/Bloomberg via Getty Images
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A grounded Lion Air Boeing Co. 737 Max 8 aircraft sits on the tarmac at terminal 1 of Soekarno-Hatta International Airport in Cenkareng, Indonesia, on Tuesday, March 15, 2019. Sundays loss of an Ethiopian Airlines Boeing 737, in which 157 people died, bore similarities to the Oct. 29 crash of another Boeing 737 Max plane, operated by Indonesias Lion Air, stoking concern that a feature meant to make the upgraded Max safer than earlier planes has actually made it harder to fly. Photographer: Dimas Ardian/Bloomberg via Getty Images
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Rescuers work at the scene of an Ethiopian Airlines flight crash near Bishoftu, or Debre Zeit, south of Addis Ababa,  Ethiopia, Monday, March 11, 2019. A spokesman says Ethiopian Airlines has grounded all its Boeing 737 Max 8 aircraft as a safety precaution, following the crash of one of its planes in which 157 people were killed. (AP Photo/Mulugeta Ayene)
Mulugeta Ayene/AP
Rescuers work at the scene of an Ethiopian Airlines flight crash near Bishoftu, or Debre Zeit, south of Addis Ababa, Ethiopia, Monday, March 11, 2019. A spokesman says Ethiopian Airlines has grounded all its Boeing 737 Max 8 aircraft as a safety precaution, following the crash of one of its planes in which 157 people were killed. (AP Photo/Mulugeta Ayene)
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Boeing CEO Dennis Muilenburg warned investors Wednesday that the company might need to further slow or temporarily halt its 737 Max production.

Boeing has continued to build the 737 Max, its bestselling jet, although at a slower pace. The plane has been grounded since mid-March because of two fatal crashes that killed more than 300 people.