The class/nobility theme is quite remarkably played out in Grand Illusion.
The French aristocrat (who calls his wife by Vous) and the German aristocrat
both use the new airplanes as an extension of cavalry/chivalry.  Gabin is
an example of the (recently) educated working class who becomes able to
become higher (military) rank because of his skills.
The death of the French aristocrat and Gabin's survival with the wife of
the dead German soldier are strong social commentary.
Ed Haupt