Boeing investors got an advance warning of the supply chain issues when Tom Gentile, CEO of key supplier Spirit AeroSystems ( SPR 2.98% ), a manufacturer of aerostructure and components on the Boeing 737 MAX and other aircraft, told investors it expected to maintain a rate of 31 737 MAX aircraft a month. Previously, Spirit had expected to ramp up production in the fall, leading to a total of 350 for the year, but Gentile now expects just 315.