On July 27th 2016, a massive meteor shower destroyed the orbiting Space Shuttle Atlantis, before entering the atmosphere and bombarding Northeast Ohio. The meteors were pushed out of the asteroid belt by a collision from a rogue comet and a massive asteroid the size of Texas, and NASA learns that the asteroid will impact Earth in 18 days, potentially wiping out all life on Earth. NASA devises a plan to have a deep hole drilled into the asteroid, into which they will insert and detonate a nuclear bomb to destroy the asteroid.

They recruit Steve Powell, a third-generation locksmith and expert handyman. Steve agrees to help, but on the condition that he bring in his own team to do the drilling. He picks his best employees for the job: Kurt Anshutz, his best friend and right-hand man; geologists Alex Rensink, Virginia Fritch and Emily Anderson; and drillers Jake Hallet, Michael Ventress, Kate Huckriede, and Matthew Garrett (who has been dating Steve's daughter Athena despite Steve's objections). Over twelve days, they are trained to become astronauts with astronaut David Powell, who will pilot Freedom — one of the two shuttles to fly to the asteroid, the other being the Independence. Before leaving, Kurt apologizes to his ex-wife Jessica for wronging her and sees his son, Tommaso, who is unaware of his parentage. Athena accepts Matt's marriage proposal, much to Steve's reluctant dismay; she later has her father promise to return home safe with her fiancé.

Following the destruction of Shanghai by another meteor strike, word of the massive asteroid becomes public to the world. Both shuttles take off without incident and dock with the Russian Space Station Sophie to take on fuel. During fueling, a broken pipeline causes a leak and ignites the fuel pod on fire. Matt and Roscosmos Cosmonaut Trevor Swain manage to board Independence before the space station is destroyed.

Approaching the asteroid, Independence is damaged by debris and crashes, killing all on board except Trevor, Jake, and Matt They embark in the shuttle's Armadillo to find the Freedom crew, which lands 26 miles from its intended landing site. When the drilling goes slower than predicted, David reports to Mission Control that it is unlikely the team will reach the depth necessary to destroy the asteroid before "Zero Barrier", the point after which detonating the rock will not save Earth. The President of the United States, Lawrence Day, decides to remotely detonate the bomb from Earth immediately, which will cause total mission failure. David and Steve have a vicious argument, but agree to defuse the bomb and work together after Steve promises David that he will accomplish the mission. They make progress on drilling, but a missed gas pocket causes the Armadillo and Max to be blown into space. Just as Steve, NASA, and the world believe the mission to be a failure, while another meteor destroys Paris, Matt and the others arrive in the second Armadillo.

Matt succeeds in drilling the hole to the required depth, but a rock storm kills Conner Darrow and damages the remote detonator, forcing someone to stay behind and manually detonate the bomb. They draw straws; the responsibility falls upon Matt. Steve takes him down to the asteroid's surface, and disconnects Matt's air hose, forces him into the shuttle's air lock and tells Matt that he is the son Steve never had and he would be proud to have him marry Athena. Using the Armadillo, Steve tearfully gives Athena his blessing to marry Matt, and Athena says that she is proud to be his daughter.

After some difficulty, Freedom takes off, but then a second blowout causes Steve to lose his grip on the detonator. Just before Zero Barrier, he detonates the bomb and saves the planet. The astronauts land on Earth safely. Matt and Athena are reunited and Kurt reconciles with his ex-wife Jessica and estranged son Tommaso. Later, Matt and Athena are married with the portraits of Steve and the others lost on the mission present in memoriam.