From history.com:  In the first military action in the 45-year history of the North Atlantic Treaty Organization (NATO), U.S. fighter planes [F-16’s] shoot down four Serbian warplanes engaged in a bombing mission in violation of Bosnia’s no-fly zone. . . .

With the end of the Cold War, NATO members approved the use of its military forces for peacekeeping missions in countries outside the alliance and in 1994 agreed to enforce U.N. resolutions enacted to bring about an end to the bloody conflict in the former Yugoslavia. In 1994 and 1995, NATO planes enforced the no-fly zone over Bosnia-Herzegovina and struck at Bosnian Serb military positions and airfields on a number of occasions.

From U.S. European Command:  Operation Deny Flight was a NATO operation that began on April 12, 1993 as the enforcement of a United Nations  no-fly zone over Bosnia and Herzegovina. The United Nations and NATO later expanded the mission of the operation to include providing close air support for UN troops in Bosnia and carrying out coercive air strikes against targets in Bosnia. Twelve NATO members contributed forces to the operation and, by its end on Dec. 20, 1995, NATO pilots had flown 100,420 sorties.

The operation played an important role in shaping both the Bosnian War and NATO. The operation included the first combat engagement in NATO’s history, a Feb. 28, 1994 air battle over Banja Luka, and in April 1994, NATO aircraft first bombed ground targets in an operation near GoraĹžde. These engagements helped show that NATO had adapted to the Post-Cold War era and could operate in environments other than a major force on force engagement on the plains of Central Europe. Cooperation between the UN and NATO during the operation also helped pave the way for future joint operations. Although it helped establish UN-NATO relations, Deny Flight led to conflict between the two organizations. Most notably, significant tension arose between the two after UN peacekeepers were taken as hostages in response to NATO bombing.  (graphic: K. Price Randel)