The Edge (1985)

The US decides to change the world's balance of power by providing Finland with a nuclear bomb called TISWEN II. The plan is to transport the bomb by plane, but disaster happens as the flight is hijacked by a terrorist group named "The Brokerage". The terrorists plan to sell the bomb to Libya. In the meanwhile Russia has found out about the plan and threatens to shoot down the plane. Which could mean the start of WW3.