By the start of the United States Afghan campaign in 2001, the USAF had acquired 60 Predators, but lost 20 of them in action. Few if any of the losses were from enemy action, the worst problem apparently being foul weather, particularly icy conditions. Some critics within the Pentagon saw the high loss rate as a sign of poor operational procedures. In response to the losses caused by cold weather conditions, a few of the later USAF Predators were fitted with de-icing systems, along with an uprated turbocharged engine and improved avionics. This improved "Block 1" version was referred to as the "RQ-1B", or the "MQ-1B" if it carried munitions; the corresponding air vehicle designation was "RQ-1L" or "MQ-1L".