Most likely there was an update (or similar) to the plane that did not complete, and hence the exterior model is missing.
My advice would be :-
(ie what i would do, and have done in the past for similar issues),
is to quit MSFS, then manually delete the plane from MSFS , and when you restart MSFS, it will either re-install, OR you will find it available to re-Install from within MSFS.