The ship was steered by an autopilot that relied on position information from the Global Positioning System (GPS).
• If the GPS could not obtain a position from satellites, it provided an estimated position based on Dead Reckoning (distance and direction traveled from a known point).
• The GPS failed one hour after leaving Bermuda.
• The crew failed to see the warning message on the display (or to check the instruments).
• 34 hours and 600 miles later, the Dead Reckoning error was 17 miles.