Russia is currently pushing out its surveillance in every direction. It's not breaching other countries airspace at this time, just pushing its limits. That's what happened here. That's what's been going on in the Aleutian Islands.
Edit: Nevermind, they've started breaching Japan's airspace.
yeah I feel the very moment they cross the line you have to launch given the way russia acts. Not doing so is basically asking for further encroachment. Same with china really.