While fixing a satellite in orbit, the Space Shuttle Atlantis is destroyed by a meteor shower, killing the entire crew. Meteorites then bombard New York City and several other parts of the world, and NASA discovers that an asteroid the size of Texas, traveling at 22,000 miles per hour, will collide with Earth in 18 days, effectively destroying the planet. The scientists at NASA - in cooperation with the Russian, Japanese and other European space agencies - plan to detonate a nuclear bomb at a precise point under the asteroid's surface which will split it in two, and cause it to miss the Earth. However, the bombs must be planted at least 800 feet below the surface within eight hours of landing, and no later than four hours before the Earth impact. The mission is not revealed to the public, fearing panic.
NASA locates Harry Stamper (Bruce Willis), because he could help them drill a hole on the asteroid. When invited to NASA, Harry brings his daughter Grace (Liv Tyler) to keep her away from A.J. (Ben Affleck), a young, rambunctious member of his crew who, he has just discovered, has been sleeping with her. This disappoints and infuriates Harry because he did not want his daughter to marry an oil driller like himself or remain in the blue collar life. Head of NASA Dan Truman (Billy Bob Thornton) informs Harry of the dire situation. Harry recognizes that he and his crew must accompany the astronauts to ensure the job is done properly. After Harry's crew (Jayotis "Bear" Kurleenbear, Max Lennert, Rockhound, Oscar Choice, Charles "Chick" Chapple and some others) is collected and NASA acquiesces to their demands, they are put through a 12-day training program and outfit a drilling rig with the proper equipment.
After a meteorite strikes Shanghai, China, destroying the city and causing a tsunami, the incoming asteroid and pending mission are revealed to the world. Two military shuttles, Freedom and Independence, are launched and dock at a Russian space station (crewed by Lev Andropov) to refuel with liquid oxygen propellant. A.J. encounters a problem stopping the pumps after the ships' tanks are full and the station explodes. The crews and Lev Andropov escape. Later, the two shuttles perform a high G-force powered slingshot procedure around the Moon, traveling at 22,500 miles per hour to intercept the asteroid.