What was found
AFTER TAKEOFF MAGENTA LINE SHOWED TURN TO NORTHWEST INSTEAD OF SOUTH. SHOWED UNABLE RNP, GNS SHOWED APPROX 5000 NM OFF. CHECKED POSITION & WAY POINTS PRIOR TO PUSHBACK, ALL CHECKED GOOD. MAGENTA LINE LOOKED GOOD, MAP & PLAN HEADING SHOWED OFF APPROX 40 DEG IN AIR. RETURNED & FOUND ALL THREE IRU'S IN DISAGREE FOR ALIGNMENT. GNS SHOWED CORRECT LATERAL & LONGITUDE. REALIGNED ALL IRU'S IAW AMM 34-43-00-5. ALL LATERAL & LONGITUDE REFERENCES AGREE, GNS & IRU. AIRCRAFT OK FOR SERVICE.