The FAA released AD 2001 06 22 a few months ago. This AD grounds all B17 Flying Fortresses until inspections of the wing spar have been carried out:
SUMMARY: This amendment adopts a new airworthiness directive (AD), applicable to all Boeing Model B-17E, F, and G airplanes, that requires inspections to detect cracking and corrosion of the wing spar chords, bolts and bolt holes of the spar chords, and wing terminals; and correction of any discrepancy found during these inspections. This amendment is prompted by reports of cracking and corrosion of the wing spar. The actions specified by this AD are intended to prevent reduced structural integrity of the wing of the airplane due to the problems associated with corrosion and cracking of the wing spar.
