An NTSB safety alert issued late last month urges pilots to activate leading-edge de-ice boots as soon their airplane enters icing conditions, “unless the aircraft flight manual or the pilot’s operating handbook specifically directs not to activate them.” According to NTSB acting chairman Mark Rosenker, “This Safety Alert is intended to increase the visibility of airplane icing issues and address procedures taught regarding the accumulation of ice before activating de-ice boots.” Some of the highlights of the safety alert include noting that as little as a quarter-inch of ice can be deadly as it can increase the stall speed 25 to 40 knots and that early activation of the de-ice boots limits the effects of leading-edge ice and improves the operating safety margin.