Summary
We propose to adopt a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This proposed AD was prompted by reports of cracks found in the lower chord of the left wing rear spar. This proposed AD would require repetitive inspections for cracking of the lower chord of the rear spar and lower aft skin at wing buttock line (WBL) 157 and applicable on-condition actions. We are proposing this AD to address the unsafe condition on these products.