Possibly part of the same bug: Non-airport bound aircraft that are sitting on a dock don't count as 'using up' a dock, and you get the same behaviour - you can queue a final aircraft for which there is no space and it will never complete construction.
Possibly part of the same bug: Non-airport bound aircraft that are sitting on a dock don't count as 'using up' a dock, and you get the same behaviour - you can queue a final aircraft for which there is no space and it will never complete construction.