LONDON (Reuters) -Boeing shares listed in Frankfurt fell almost 8% early on Monday after the U.S. Federal Aviation Administration ordered the temporary grounding of some Boeing (NYSE:) 737 MAX 9 jets.

A piece of fuselage tore off the left side of an Alaska Airlines jet on Friday as it climbed following takeoff from Portland, Oregon, forcing pilots to turn back and land safely with all 171 passengers and six crew on board.

Boeing competes with Airbus, which has expanded its market share since two Boeing MAX crashes in 2018 and 2019 that killed nearly 350 people and led to the MAX's worldwide grounding for 20 months.

Airbus shares rose 1.25% early on Monday. The company will announce this week that it delivered 735 planes last year, beating Boeing to remain the world's largest planemaker for the fifth year in a row, industry sources said. Airbus has declined to comment on its annual performance ahead of the commercial update on Jan. 11.

Boeing's Frankfurt shares pared some early losses to stand 6.5% lower by 0835 GMT.

Jefferies said in a note that the latest Boeing incident could slow aircraft production if manufacturing and installation processes are subject to further regulatory probes.

Boeing CEO Dave Calhoun on Sunday said the firm's response to the incident was its main focus right now as regulators carry out an investigation.

The planemaker also plans to hold a company-wide webcast on safety on Tuesday to address its response. It also cancelled a leadership summit for company vice presidents previously scheduled for Monday and Tuesday.