(Reuters) -The crash of an Air India 787-8 Dreamliner jet minutes after taking off on Thursday poses a major setback for Boeing, whose new CEO has been trying to rebuild trust following a series of safety and production challenges.

The disaster, in which most of the 242 people on board were killed, tarnishes the jet’s safety record heading into the Paris airshow next week and muddies the efforts of CEO Kelly Ortberg to boost production after the plane maker hit the targets in May.

Shares were down about 4.8% and were trading at $203.55 after falling as much as 8% before the opening bell. Boeing said it was aware of the initial reports and was working to gather more information.

The London-bound plane crashed in India’s western city of Ahmedabad, authorities said, in the world’s worst aviation disaster in a decade. It was not clear what caused the crash.

Before the crash, airline bosses had been voicing greater confidence in Boeing’s rebound in deliveries and in Ortberg’s leadership after years of reputational damage for the plane maker.

Executives Were More Optimistic in a Recent Summit

At a recent summit in New Delhi, executives were more optimistic over Boeing’s crises around safety and regulation.

The widebody 787 planes, one of the most modern passenger aircraft in service, have never had a fatal crash until the Air India incident. They were grounded in 2013 due to battery issues, but no one was reported injured.

However, Boeing’s narrow-bodied 737 MAX jets were grounded for years following two fatal crashes and have faced years of scrutiny and production delays.

Last year, the U.S. plane maker came under renewed scrutiny after a door plug blew off a 737 MAX 9 mid-flight, prompting a temporary FAA grounding and fresh concerns over quality control.

Shares of Spirit AeroSystems, a key supplier, and GE Aerospace, which makes engines for the jet, also fell about 2% each.

GE Aerospace said it has activated its emergency response team and would support the investigation, but did not specify if the Air India aircraft was equipped with its engines.

The engine maker did not immediately respond to a Reuters request for comment.

“It’s a knee jerk reaction (to the incident) and there’s revised fears of the problems that plagued Boeing aircraft and Boeing itself in recent years,” said Chris Beauchamp, analyst at IG Group.

Boeing’s outstanding debt also sold off modestly after the crash. Its bonds maturing in May 2029 were trading at 88 basis points over Treasuries, or 10 basis points wider than on Wednesday, according to a bond broker.

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(Reporting by Shashwat Chauhan, Nathan Gomes and Purvi Agarwal in Bengaluru and Shankar Ramakrishnan in New York; Editing by Saumyadeb Chakrabarty and Arun Koyyur)