(Reuters) - Boeing ( BA ) said on Tuesday it delivered 33 jets in September, down from 40 plane deliveries in August, as a strike mid-month by around 33,000 U.S. West Coast factory workers weighs on output.

Boeing's ( BA ) September deliveries were up by six jets from the same month in 2023, when the U.S. planemaker handed over fewer of its strong-selling 737 MAX planes to customers as it struggled with work needed to correct a manufacturing defect.

The strike, which started on Sept 13, has halted production of the MAX, along with Boeing's ( BA ) 777 and 767 widebody jets, hitting a revenue-driver at a time when the company was already struggling with lower narrowbody production due to a quality crisis and weak margins in its defense business.

Boeing ( BA ) handed over 27 MAX jets to customers last month, including five to United Airlines, and three each to customers Ryanair, and Southwest Airlines ( LUV ), whose CEOs have expressed concern over lower deliveries.

Investors closely watch delivery numbers, as airplane makers receive the majority of payment for a jet when it is transferred to a customer. Boeing ( BA ) has said it expects a reduction in deliveries going forward due to the strike.

Boeing ( BA ) also booked 65 gross orders during September, including 54 737 MAXs and 11 777 freighters for unidentified customers. On September 19, China Development Bank Financial Leasing said its aircraft leasing unit would order 50 Boeing MAX jets.

Boeing's ( BA ) gross order total so far this year through Sept 30 rose to 315. After removing cancellations and conversions, Boeing ( BA ) posted a net total of 272 orders since the start of 2024.

Following further accounting adjustments, Boeing ( BA ) reported adjusted net orders of 121 airplanes so far this year.

Year-to-date through September 30, Boeing ( BA ) delivered 291 airplanes, including 225 MAX jets.