Belgian air exercise / airshow 1939 ?

Spring cleaning my desk over Easter I found something I had forgotten about.

It’s a presentation medal / tablet by Carlos van Dionant which has on the reverse;
Souvenir de la manifestation aerienne du
9 Juillet 1939
Le General Hieraux
Commandant L’Aeronautique Militaire
and inscribed to Major Eeles

This was S/L Henry Eeles who according Men of the Battle of Britain was at that time PA to the Chief of Air Staff. General Hiernaux was the commander of the Belgian airforce.

Does anyone have any record of the event, was this an air exercise or airshow type event ?

Jeff