Early in this investigation, the focus was on the controller. Then it switched to the heli’s altitude. Everyone said, wow, it usually take two things gone wrong to cause an accident. True enough, but now there are three things. Helicopter Route 4 specifically shows the corridor follows the extreme eastern bank of the Potomac. The collision happened closer to the western side. So we have a controller who didn’t know the heli’s real altitude, didn’t make note the heli was too far west, a heli pilot who was flying too high, and was out of position. That’s four things wrong, and any one of them could have prevented this accident. Incidentally, the further west the heli flies, the more even his legal altitude becomes an issue.