The Russians Have Shot Down Numerous US Drones Violating Crimean Airspace
And one of them, the mother of all drones, the massive Northrop Grumman RQ-4 Global Hawk, was apparently commandeered by Russian electronic warfare and landed in Simferopol
The war you don't hear about: numerous American military aircraft (albeit of the unmanned variety, though with the possibility of being armed and dangerous) have apparently been violating Russian airspace, leading to the Russians shooting - yes, shooting - them down following the refusal of the Americans to acknowledge Russian diplomatic notes of protest.
The military violation of the territory, including the airspace, of a sovereign state is ordinarily taken to be a casus belli - an act of war.
But to be fair to the Americans, they may justify their belligerent behavior, flagrantly refusing to respect Russia' sovereignty, on the basis that they do not recognize Crimea to be a part of Russia. Therefore, they do not recognize any violation of the airspace of Russia as having taken place. Rather, they would contend that the American aircraft in question were flying within the sovereign territory of Ukraine, with the permission of the government with the only legitimate authority to grant, and refuse, such permission, namely the government of Ukraine.
Nevertheless the Russians have made it clear that they consider Crimea to be a sovereign part of Russia. The Russians have made diplomatic protests over what they see as violation of their territory. The Americans have ignored them. The Russians have therefore shot down - and in once case commandeered and landed - these aircraft making incursions into their sovereign territory.
An act of war has been committed by America against Russia; and if you accept the American position, an act of war has been committed by Russia against both the Ukraine and the United States. Shots have been fired, and the Americans have lost military materiel.