Longman Dictionary of Contemporary English
Wiktionary
n. an airspace in which aircraft, especially military aircraft, are forbidden to fly
Wikipedia
A no-fly zone (or no-flight zone) (NFZ) is a territory or an area over which aircraft are not permitted to fly. Such zones are usually set up in a military context, somewhat like a demilitarized zone in the sky, and usually prohibit military aircraft of a belligerent power from operating in the region. Aircraft that break the no-fly zone may be shot down, depending on the terms of the NFZ.
No-fly zones are a modern phenomenon. They can be distinguished from traditional air power missions by their coercive appropriation of another nation’s airspace only, to achieve aims on the ground within the target nation. While the Royal Air Force (RAF) conducted prototypical air control operations over contentious colonial possessions between the two World Wars of the 20th century, no-fly zones did not assume their modern form until the end of the Persian Gulf War in 1991.
During the Cold War, the risk of local conflict escalating into nuclear showdown dampened the appeal of military intervention as a tool of U.S. statecraft. Perhaps more importantly, air power was a relatively blunt instrument until the operational maturation of stealth and precision-strike technologies. Before the Gulf War of 1991, air power had not demonstrated the “fidelity” needed to perform nuanced attacks against transitory, difficult-to-reach targets—it lacked the ability to produce decisive political effects short of total war. However, the demise of the Soviet Union and the rise in aerospace capabilities engendered by the technology revolution made no-fly zones viable in both political and military contexts.
Usage examples of "no-fly zone".
Without the northern no-fly zone, and with the United States explicitly forswearing interference in Iraq's internal affairs, the Kurds would have no friends but the mountains, as their traditional saying bemoans.
In June of '95, the Air Force had lost a scout pilot in NATO's no-fly zone, near the Croat border.
The plane will move north up through Kuwait, and then through the no-fly zone in Iraq.
Now she realized that she should have caught on when she saw them flying: that had to be illusion, not reality, here in the no-fly zone.
I'm scrambling an F-15 fighter squadron to join you in the next few minutes and I want a no-fly zone over the state of Colorado.
It was good enough, in fact, that all seven of the pirate crews working out of Vlarnya declared it-and the fields where it grew the things that went into the ale-a no-fly zone to reduce the chances of an aerial accident destroying it.
With NATO currently enforcing a no-fly zone over Bosnia, an attack by submarine had struck Khan as the ideal way to get his revenge on Hunyadi without having to fight his way through contested airspace or war-torn terrain.