Jack Traven is a young S.W.A.T cop in the Los Angeles police department. One morning Jack witnesses a bus explode and Jack receives a phone call from Howard Payne, a retired Atlanta bomb squad explosives expert gone bad, Payne has wired a passenger bus to explode, where if the bus speeds at 50 miles per hour the bomb is armed, if the bus slows down and drops below 50 miles per hour the bus will explode. Payne demands $3-millions dollars and Jack or any of the passengers tries to get off the bus, he will detonate the bomb. Managing to get on the bus, Jack with help of one of the passengers, Annie who is driving the bus when the driver is injured, tries to keep the passengers alive and guide the bus through the traffic, and keep the bus speeding at 50 miles per hour, as the S.W.A.T team and Jacks partner, explosives expert Harry Temple set to discover Paynes location and find a way to disarm the bomb before the bomb explodes when the bus runs out of gas.