Spirit AeroSystems became the latest supplier to Boeing’s troubled 737 Max to warn about the impact of the aircraft’s worldwide grounding as it suspended its full-year guidance and halted share buybacks. The US company is Boeing’s biggest parts supplier and produces 70 per cent of the 737’s aerostructure, including the entire fuselage, the thrusters and the flaps and slats of the wings. Despite reporting strong first-quarter results, Spirit said Boeing’s decision to cut the Max’s monthly production rate from 52 to 42, and not ramp up to 57 by June as expected, meant its prior guidance no longer stood.