The FAA has issued a final rule superseding an existing airworthiness directive (AD) for all Pilatus PC-12s, PC-12/45s, PC-12/47s and PC-12/47Es. Since the issuance of AD 2009-14-13 Pilatus has issued revisions to the limitations section of the airplane maintenance manual to include an inspection of the wing main spar fastener holes at rib six for cracks. The action was prompted by a crack found on one wing, and a more restrictive airworthiness limitation was introduced in that manual. The document includes the maintenance instructions and/or airworthiness limitations developed by Pilatus and approved by the EASA. Failure to comply with these instructions and limitations could potentially lead to an unsafe condition.