Converting campaign to coop

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" then open each mission and deselect the player aircraft and then change all of the ai aircraft in the missions to flyable."

Not necessarily. In most coops you will have a mix of both flyable and AI planes.

Depending on the mission, you will need to decide which planes will be flyable and which will be AI. Simply making every plane flyable is not the best idea for a coop. Some thought has to be put into it.

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