A). SERVICE LETTER MOS WING AND HORIZONTAL STABILIZER INSPAR FINISHES (ORIGINALLY REPORTED AS ATA 5180-21). SERVICE LETTER MOS BOEING APPROVAL OF AIRPLANE STRUCTURAL REPAIR AND MODIFICATION DATA. SERVICE LETTER MOS (s) SL 737-SL-51-027 REV. D BOEING COMMERCIAL AIRPLANES REVIEW AND DELEGATED APPROVAL OF AIRPLANE STR