Safety experts recommend that the engines on Boeing’s troubled 737 Max airplanes be modified quickly to prevent smoke from filling the cockpit or cabin after a safety feature is activated following a bird strike.

The National Transportation Safety Board warned that certain CFM engines installed in some Boeing 737 Max jets may feed smoke into the cockpit or cabin after a bird strike.

The NTSB issued an “urgent safety recommendation” related to the engine on the 737 MAX after two incidents where smoke entered the cabin.