The letter sent out reminds owners that Autopilot is strictly a driver assistance feature and still requires the driver's full, undivided attention. That's how Tesla says it describes the feature, but there's concern that drivers aren't staying completely alert while using Autopilot.
The fatal crash, which took place in May, isn't the only Autopilot-related incident -- a second, non-fatal accident took place in July, but it's not clear yet that Autopilot was at fault. Another crash took place in China in August, and the cumulative effect of these incidents has led to questioning on how exactly the company messages Autopilot to its customers. Indeed, the name itself makes it sound as if the car can drive itself -- but that is definitively not the case.