Boeing starts building first 737 MAX jet on schedule

The first spars, or large structural wing pieces that run perpendicular to the fuselage, were loaded on May 29, said Keith Leverkuhn, vice president and general manager of the 737 MAX program.

He added that the first of the new planes is due to be completed before year end, with flight testing to start in early 2016.

Boeing is using new robotic machines, which began making wings for current generation 737s earlier this year, to assemble the MAX wings. The machines automate about 90 percent of the wing assembly process, up from 70 percent on older, legacy machines that Boeing has used for decades, Boeing said.

Boeing has received 2,724 orders for the next-generation plane, being developed to compete with Airbus' a320neo.

Boeing shares rose 2.1 percent to $144.28 on the New York Stock Exchange.

(Reporting by Alwyn Scott; Editing by Alden Bentley and Richard Chang)