Boeing Chief Financial Officer Brian West said a strike that began on Friday would impact aircraft deliveries and “jeopardize” the company’s recovery, just hours after factory workers walked off the job and overwhelmingly rejected a new labor contract.

West said the financial impact of the strike would depend on its duration, but it would affect production of its best-selling planes. At an industry conference on Friday, West declined to say whether the company could reach a production rate of 38 737 Max planes per month by year’s end.

Jefferies aerospace analyst Sheila Kahyaoglu had previously estimated that a 30-day strike could cost Boeing $1.5 billion.

West said Boeing would initially focus on “cash conservation measures,” adding that new CEO Kelly Ortberg would work to restore relations with the union.

Boeing and the International Association of Machinists and Aerospace Workers unveiled a tentative collective bargaining agreement on Sunday that calls for wage increases of 25 percent over four years and other improvements in health and pension benefits. But workers had demanded a 40 percent increase, arguing that it would not cover the increased cost of living.

94.6% of workers in the Seattle area and Oregon rejected the proposal and 96% favored a strike.

They stopped working after midnight on Friday.

The last strike by Boeing engineers took place in 2008 and lasted almost two months.

The potential production disruption comes as the manufacturer faces a series of problems as it struggles to ramp up production and restore its reputation following safety crises.

A burst door stopper on a nearly new Boeing 737 Max 9 in January prompted the Federal Aviation Administration (FAA) to prohibit Boeing from increasing production of its Max aircraft and increasing inspections at its production facilities until the regulator was satisfied with safety and quality procedures there.

An FAA spokeswoman told CNBC on Friday that the agency would keep its inspectors at Boeing facilities during the strike.