This is primarily a long-standing dispute between Russia and the Ukraine.
America has become more and more involved in the last couple of years.
Russia has used Crimea as their naval base since the days of the old Soviet Union and before. It would be as if someone threatened our Norfolk Naval Base. We would protect it at all costs. So it is with the Russians. Perhaps Putin's dream is to restore the old Soviet Union?
It's a complicated and complex story with their natural resources. Russia sells a lot of natural gas to Europe. However, most of the pipelines go thru Ukraine. They have possession of the infrastructure but they (Ukraine) also get their gas from Russia. And they have had incidents where their gas was cut off because they owe the Russians about a billion dollars on their gas bill. Russia has increased the prices at will.
But Ukraine supplies Crimea with energy and fast-speed Internet. That is their leverage that they have on the Russians - other than the pipelines - and this is maybe the root of the crisis?
Since Russia is intent on protecting what they perceive as theirs, they have sent all sorts of weaponry to the border of Eastern Ukraine and Russia and they have hired their own rag-tag bunch of mercenaries to fight for them inside the Ukrainian border and are training them to protect their borders and the airspace over Crimea and Eastern Ukraine.
It would not be surprising if Putin ordered the plane shot down, just to send a message to America and the West. "If you are thinking of bringing in your caterpillar drones, we will shoot them down. And we will shoot down whatever else enters our airspace..."
This is serious business but I don't know if America wants to get too close to either side in this conflict? Maybe they have already made promises that they cannot keep?