Boeing Co (NYSE:BA) stock flew lower Monday as it emerged that the group was repportedly mulling plans to raise more debt amid the rising costs of grounding its 737 MAX jet.

Boeing is still working to ready the 737 passenger planes for service after two horror crashes within five months killed 346 people.

Boeing faces compensation claims from airlines and families of the victims and debt has reportedly doubled as MAX receipts fell, forcing it to maximize revenue from outside plane sales.

In January, the firm stopped production of the plane, which has lowered some costs but has pushed back the likely date at which payments for finished planes would resume.

The Wall Street Journal cited people familiar with the situation saying that Boeing is considering plans to raise more debt to bolster its strained finances.

Analysts expect Boeing to raise as much as US$5 billion in additional debt to help cover costs that could exceed $15 billion in the first half of this year, according to the WSJ.

As well as laying out for maintenance for the MAX’s stalled production facilities and finished planes, Boeing also aims too close its US$4 billion acquisition of an 80% stake in the Brazilian plane maker Embraer SA’s commercial airliner business.

Boeing also has to repay some existing debt and fund shareholder dividends.

It comes after Greg Smith, Boeing’s chief financial officer and now interim CEO, said last October that it did not expect to have to resort to any unspecified “levers” to improve its finances.

Boeing had about $20 billion in available funds at the end of the September quarter, according to the company’s financial statements.

Boeing shares in New York shed 1.38% to US$328.17.