How does it end

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They leave the meatpacking plant, en route to the airport.

While on the road, they see the vehicle Garner et al. were driving abandoned. Tom determines they are still headed there and that they can get there before Garner et al., which they do.

Garner roughs up and threatens Carly's brother (scientist, can't remember name, sorry). The brother gets on the radio to communicate with the plane. The plane indicates they're in trouble and eventually put out a mayday call. The transmission is cut and the viewer is led to believe the plane has crashed (or, like the cars, exploded). The brother freaks out for a bit, but then seeing the reaction this incited from Garner, he begins to fake a communication with the plane, perpetuating the belief that all is well, the plane will land an they'll get to the arctic.

After the brother gets off the radio, he sees Tom and, while Garner is distracted, he begins to slowly walk away. One of Garner's thugs, seeing this, starts the final battle. The brother (might have been shot, I think but I don't recall), sneaks out of the line of gunfire, then realizing this is all turning ugly, comes out screaming "There is no plane, there is no plane!"

At this point, Garner's thugs, realizing they have nothing more to fight for, walk out of the hangar. Garner has been roughed up, perhaps even shot, and seemingly disarmed. As Tom and Bonnie tend to CJ, who was shot in the firefight, Garner reaches down towards his ankle and withdraws a pistol. Bonnie sees this, alerts Tom, who wheels around and fires, killing Garner.

Moments later, you hear raindrops on the roof of the building. Kimberly steps outside and soon after finds herself in a downpour, the message here being because there is now rain, they have survived. (See other thread on raindrops to understand why this is factually inaccurate.)

Hope this helps.