That means airspace.

As in: Time To Acknowledge Ukrainian Airspace Is As Dangerous As 1961 Berlin.

The tools are different, and the location has changed, but NATO and Russian President Vladimir Putin are engaged in a repeat of an epic October 27, 1961, Cold War standoff, when combat-ready American and Soviet tanks faced off in Berlin. Back then, the Soviets were reneging on Post World War II agreements that guaranteed the wartime allies unfettered access to East Berlin, and America successfully sent tanks to the border crossings to maintain those rights.

Today, the Ukraine border is a modern-day Checkpoint Charlie, and, instead of tanks, American reconnaissance platforms are confronting Russian anti-aircraft missile batteries and fighter aircraft. And, rather than backing out of post-World War II access agreements, Russia is set to renege on a guarantee of Ukraine’s sovereignty.