I don't think the latter is completely true. JWST can capture a smaller range of infrared for starters, and is obviously impossible to change, whereas an airbor

I don't think the latter is completely true. JWST can capture a smaller range of infrared for starters, and is obviously impossible to change, whereas an airborne platform can carry additional instruments if needed. And for observations in the solar system, the ability to move can be helpful too. E.g. if an occlusion is visible anywhere on earth SOFIA can move there, JWST is either in the right spot by accident or is no.