Maastricht Treaty comes into force
The Maastricht Treaty that created a common currency, the Euro, for European Union countries came into force

United Airlines Flight 629 blows up over Colorado
A bomb hidden in checked luggage of United Airlines Flight 629 exploded over Longmont, Colorado killing all 44 people on board.

First large hydrogen bomb tested by the U.S.
The bomb, codenamed Mike, was part of Operation Ivy and was tested in the Eniwetok atoll in the Marshall Islands.

First bomb dropped from an aircraft
Prior to this, bombs were dropped using unmanned balloons. The first bomb launched from an aircraft was used by the Italians in the Italo-Turkish War.