Independence Day(1996)

Finally, the question "are we alone in the universe" has been answered. People react with fear, wonder, and excitement while dozens of fifteen mile long ships silently take up positions over cities across the globe. When MIT graduate turned satallite repair man David Levinson discovers a hidden signal being used by these spacecraft it leads to a most terrifying conclusion...the aliens are primed for attack, and there are only hours left until the countdown is over. Few escape the near-total destruction of Earth's major cities; and now they must find a way to fight an enemy that their weapons cannot touch, their technology cannot match, and their numbers cannot overwhelm.