P300 currently have a non immediate SB regarding corrosion in replaceable parts. Our maintenance is expecting for that to become an immediate SB or even an AD. The time it will take to replace those parts on our 8 p300 is what he is regarding as grounding the fleet. Last I heard one of our airplanes is undergoing compliance with this SB and the entire fleet will be cycle through maintenance to ensure compliance. All efforts will be to ensure safety and minimize operational impact.