When instructing Jack how to operate his parachute, the leader of the Flying Elvises (Utah chapter) tells Jack to pull the yellow lever. He then tells him if his chute doesn't open, he is to pull the red lever to activate the reserve chute. After Jack jumps, he pulls the yellow lever and then immediately pulls the red. According to the Flying Elvises leader, this should have activated both parachutes.
When Jack is on the plane with the Flying Elvises and learning how to use the parachute, it is daylight outside as seen through the windows of the plane and the interior of the cabin is full daylight. When they get up to jump, just minutes later by the film's time line, it is completely dark outside and the cabin lights are on inside the plane.
When learning the parachute, Jack is told to pull the yellow handle for his main chute and if that didn't open, to pull the red handle for the auxiliary chute. He ends up pulling "Yellow then Red" which would deploy both chutes. Having both chutes deployed would be dangerous and impossible to control.