A new airworthiness directive (AD 2003-09-10) requires operators of the Premier I to modify the aft power-distribution box and aft ram-air duct. The FAA said the AD is the result of two incidents involving temporary loss of all attitude display data, apparently from moisture entering the distribution box through the aft ram-air duct. Compliance is required within 10 hours time in service after May 13, the effective date of the directive.