Eric Wicksell is suing Bombardier for negligence, claiming the Challenger 601 is defective because operating and training manuals didn't disclose what he alleges is the twinjet's high susceptibility to icing. Wicksell was the copilot of the Challenger 601 involved in a crash at Montrose Regional Airport, Colo., on Nov. 28, 2004. Three people were killed in the accident, including a son of NBC Sports executive Dick Ebersol. Three others, including Wicksell, were seriously injured. Although the NTSB held Wicksell partially to blame for the crash, in its study of the accident the Safety Board said, "For many years we have been dealing with the fact that aircraft such as the Challenger with so-called "hard wings" [that is, those without leading-edge high-lift devices] have been found to be more susceptible to the effects of icing." The NTSB determined the probable cause of the accident to be "the flight crew's failure to ensure that the airplane's wings were free of ice or snow contamination that accumulated while the airplane was on the ground, which resulted in an attempted takeoff with upper wing contamination that induced the subsequent stall and collision with the ground."