This is what I'm referring to:
http://www.firstworldwar.com/source/germandeclarationofwar_france.htm
The German administrative and military authorities have established a certain number of flagrantly hostile acts committed on German territory by French military aviators.
Several of these have openly violated the neutrality of Belgium by flying over the territory of that country; one has attempted to destroy buildings near Wesel; others have been seen in the district of the Eifel; one has thrown bombs on the railway near Carlsruhe and Nuremberg.
I realize that Germany likely intended to declare war on France after their declaration of war against Russia, but I'm wondering if the pretext had some basis in reality.
Searching for this, I have found this short entry on a site dedicated to British airforce history, which seems legit. It seems that the German claims of French aerial incursions are largely thought of as honest mistakes, possibly lies, nowadays. I have read stories about French planes in German airspace during the crisis before, but these were always from diaries and based on civilian hearsay, most possibly the kind of hysterical balderdash that circulates in tense situations like these.