The advance payment from Boeing is a significant financial boost for Spirit Aerosystems, likely improving its cash flow and financial stability in the short term. This influx of cash could be seen positively by investors, potentially leading to a short-term uptick in SPR's stock price.

While the advance payment is a significant outflow of cash for Boeing, it demonstrates a commitment to maintaining its supply chain and meeting contractual obligations. This move could reassure investors about Boeing's operational stability, but the financial impact of this cash outflow is neutral in the short term as it reflects a reallocation of funds rather than a loss.