For the Luftwaffe the answer is: That depends on what the crew is wearing. Medals were to be worn on the standard uniform jacket or the leather jacket which was used by many fighter pilots. This means if the crewman/pilot doesn't wear a flightsuit above medals (which weren't that numerous, yet) would be visible. However if he wore a flightsuit no medals would be visible.
The same is true for rank insignia. The epaulettes and collar patches were only present on the standard uniform jacket, the leather jacket was often (or even mostly) modified to carry the epaulettes but not the collar patches.
On flightsuits none of these were present and rank was signified by simplified patches on the upper sleeve.
Edit: Additionally some units which bore a traditional name were entitled (required?) to wear a cuff title on the right sleeve. Units, cuff titles and application guide can be found here:
http://www.xs4all.nl/~rhorta/jgcuff.htm