> As the plane passed 39 000 feet, the stall and overspeed warning indicators came on simultaneously—something that’s supposed to be impossible, and a situation

> As the plane passed 39 000 feet, the stall and overspeed warning indicators came on simultaneously—something that’s supposed to be impossible, and a situation the crew is not trained to handle. But it is not impossible at all! That's called the "coffin corner". All flight crews are aware of it.