Do you remember when the Southwest Airlines 737 decompressed after a hole blew out of the top of the fuselage in April 2011? FAA issued various actions after that incident and today it revised the AD mandating 737-300, -400 and -500 inspections in the crown area of the fuselage.
The new airworthiness directive (2012-26-02) adds more inspections, requires additional repairs and reduces AD compliance times based on new reports of cracking near the lap joints in the upper fuselage.
The new AD appears to be largely based on several comments from Boeing and Southwest Airlines and takes effect on Feb. 6.
The FAA's aircraft certification services manager issued the AD on Dec. 12 but it didn't hit the Federal Register until today, which explains the 2012 AD date.