Boeing stock dropped in late trading Wednesday after management made comments at an investor conference. Investors hoped for better news about 737 MAX production.

Shares of the airplane maker traded as low as $197.01 and closed down 3.7% at $210.96, while the S&P 500 lost 0.4%.

Production of the 737 MAX was "not stable at 47 a month," said CEO Kelly Ortberg while speaking at a Morgan Stanley conference. It was taking a little longer than expected to ramp and stabilize production, he added, with wing production an issue.

Ortberg and CFO Jay Malave also spoke about certification of new jets, Chinese demand, union negotiations, and other issues. The MAX, however, was the big takeaway.

Production is of paramount importance for investors. Boeing delivered 806 planes in 2018, the year before the second tragic 737 MAX crash. Since then, annual deliveries have averaged roughly 400 a year.

Fewer planes mean less free cash flow. Boeing is expected to deliver about 670 planes in 2026 and generate free cash flow of about $2 billion. That isn't the endgame for investors, though. By 2028, deliveries are expected to top 800 jets, generating free cash flow of about $10 billion.

Another MAX production hiccup might not threaten Boeing's long-term delivery and cash flow performance. Still, it makes investors nervous.

Wednesday's losses leave Boeing stock down about 6% over the past 12 months and down 13% over the past month. Higher oil prices have also weighed on the aerospace sector. Jet fuel is a significant cost for airlines, and persistently high prices can impact demand for air travel and new jets.