Boeing has decided to keep 737 jet production below 38 per month and will only accept a fully conforming fuselage from supplier Spirit AeroSystems , CFO Brian West told analysts on Wednesday.

Shares of the planemaker fell 2.8% in premarket trading.

Manufacturing quality at both Boeing and the supplier are facing increased scrutiny following a Jan. 5 incident in which a door plug blew off a 737 Max 9 plane mid-flight.

West told a Bank of America conference that the company's cash burn in the first quarter will be somewhere between $4 billion and $4.5 billion, "higher than we originally planned back in January."

The cash burn is due to a combination of lower deliveries, lower volume at its commercial division along with some working capital pressures. (Reporting By Abhijith Ganaparavam in Bengaluru and Allison Lampert in Montreal; Editing by Anil D'Silva)