Prior to Ponch jumping from the CHP airplane, the plane's position behind the truck and the altitude of the plane varies from scene to scene.
Jon is shown just a few hundred feet behind the economy car with the robbers inside, which is no match for the KZ1000 police motorcycle. They flee into a parking/storage lot and Jon is then shown approaching from the other direction from which they were both traveling.
Janos exclaims "Did you see that? That was incredible" when Ponch jumps on the back of the truck. But it would have been impossible for either he or the passenger to see Ponch jump.
Grossman is shown in the CHP airplane over the Queen Mary just prior to the robbery, but the CHP airplane disappears during the pursuit, when it would have been used to track the robbery vehicle.