Boeing Co managed to hand over 33 aircraft to customers in September, when a strike shut down large parts of its manufacturing, while warning that the work stoppage at its main production hub in the Seattle area will reduce future deliveries.

The aircraft handed over last month had already been cleared by US regulators prior to the strike by 33,000 members of International Association of Machinists and Aerospace Workers, who walked off the job on Sept 13, closing down manufacturing across the west coast of the US. 

Boeing remains in talks with union representatives to end the strike, and the company said that it would store undelivered planes safely until deliveries can resume once a new contract has been ratified. 

The September tally included 28 of the cash-cow 737 models, four of its 787 Dreamliners and one 767 freighter, according to data posted to the company’s website. Boeing also recorded 65 gross orders during the month and no cancellations.

For the quarter ended Sept 30, Boeing delivered 116 aircraft, an improvement from the 105 jets it handed over a year earlier, and a reminder of the progress jeopardised by a strike now in its fourth week. Boeing is still building 787 Dreamliners at a non-unionised plant in South Carolina, while work has halted on the rest of its commercial line-up.

The halted deliveries have added to the financial squeeze on Boeing, which was already reeling from a near-catastrophe in January that exposed lax quality controls in its factories. Boeing slowed production, particularly the final assembly lines for its 737 Max jets, as it faced renewed scrutiny by the Federal Aviation Administration and a criminal inquiry.

So far this year, Boeing has delivered 291 aircraft, including 229 of its narrowbody 737 models. The company has booked 315 gross orders through the end of September, and has 121 net orders when including cancellations and a US accounting provision for at-risk deals.