A partially completed Boeing 737 Max airplane is pictured at the Boeing manufacturing facility in Renton, Wash., in 2015. (David Ryder/Bloomberg)

Boeing has secured a $1.5 billion line of additional credit, a sign the plane maker is taking more caution with finances as sales of the 737 Max remain on hold.

The credit facility is being arranged by banks including Citibank, JPMorgan Chase, Merrill Lynch and Pierce, Fenner & Smith, according to a regulatory filing Monday. It’s scheduled to terminate Oct. 30, with an option for Boeing to extend one additional year. The credit line expands on Boeing’s existing, unused line of $5.1 billion in credit.

Boeing’s business requires a large amount of cash to produce new planes and invest in operations, and its ability to generate cash has been stifled by the worldwide grounding of the 737 Max. The company continues to produce 42 new 737 jets a month, but cannot sell any 737 Max planes to customers until global regulators are satisfied that Boeing has improved their safety.

Companies secure access to credit as a precaution during periods when their access to cash is uncertain.

In a statement, Boeing spokesman Gordon Johndroe said the added line of credit “provides adequate financial flexibility to address financial market uncertainty, emerging business needs, as well as take advantage of potential strategic business opportunities should they arise.”

At the end of March, Boeing had a little more than $6.8 billion in cash and cash equivalents, about 10 percent less than it did the prior year.

Last week, Boeing said it paused its plan to buy back $18 billion in stock from investors, a move that freed up more cash to use in the business. Boeing also took the unusual step of withdrawing its guidance, or estimate of future financial results, because it doesn’t know how many planes it could sell this year.

Boeing’s free cash flow, a closely watched measure of how much cash the company generates after taking out the cost of capital expenditures, such as factory improvements, may fall precipitously as Boeing continues building planes that sit idle in production facilities in Renton, Wash., and elsewhere.

Cai von Rumohr, a senior analyst at Cowen, estimated earlier this month that Boeing could report zero free cash flow during the first quarter and negative free cash flow in the second quarter, before rebounding later in the year. He predicts around $12 billion in free cash flow for the whole year — well below his earlier estimate of $16 billion. Boeing had said in January that it expects free cash flow this year of between $17 billion and $17.5 billion.

Boeing has not given an estimate of how much the 737 Max grounding will cost. Airlines are incurring costs as they cancel hundreds of flights a day, which Boeing is likely to repay in the form of future discounts on new planes, analysts said. American Airlines said it expects to lose out on $350 million in 2019, assuming the grounding order is lifted by Aug. 19.

In the first quarter of the year, Boeing recorded a $1 billion accounting charge due to the costs it has incurred to change production rates.