USA Jet Airlines, flight JUS834, sustained a tailstrike while landing at the Saltillo/Plan De Guadalupe International Airport (SLW), Saltillo, Mexico. After the event, the airplane completed two additional flights before the damage was discovered by maintenance personnel. The flight was an on-demand international cargo flight from Willow Run Airport (YIP), Detroit, Michigan, to SLW.The flight crew stated that, upon arrival at SLW, they conducted an instrument landing system (ILS) approach to runway 17. A review of flight data recorder (FDR) data revealed that the autopilot and autothrottle were disconnected at about 1,400 ft above ground level (agl). The airplane was in a stabilized configuration on approach, with glideslope and localizer deviations of less than one dot. Airspeed varied by less than 5 knots and the sink rate was less than 1,000 feet per minute (fpm).The crew indicated that the flight was “slightly bumpy” on final approach with small fluctuations in airspeed. They stated that it felt as though the wind had shifted or dissipated rapidly while approaching 50 feet agl resulting in a higher-than-normal sink rate. FDR data showed that near 80 ft radio altitude (RA), the aircraft’s sink rate began to increase rapidly, indicating a sudden decrease in headwind. The control column was deflected airplane nose-up (ANU) in an apparent attempt to arrest the sink rate.FDR data showed that the control column remained deflected ANU until about 30 ft RA, when the airplane’s pitch increased to nearly 5 degrees ANU. Subsequently, an airplane nose-down (AND) column input was initiated. The airplane continued to descend at a sink rate of over 15 feet per second (fps) just before touchdown, resulting in a hard landing with a peak vertical acceleration of 3.24 gravitational force equivalent (g). The tail strike likely occurred at the Page 2 of 7 DCA23LA232touchdown point where the airplane's pitch attitude reached approximately 8 degrees, exceeding the attitude limit where the aft body of the aircraft would contact the ground once the landing gear was compressed. Based on this information, and a review of several takeoffs and landings led to the determination that the tailstrike occurred at SLW.  The crew indicated that the aircraft touched down harder than normal, that the airplane did not bounce, and they did not feel as if a tail strike had occurred.  During a post-flight inspection at SLW, the crew stated that they did not observe any damage to the fuselage and the tail skid assembly's tailstrike indicator was in a horizontal position (parallel to the fuselage), indicating a tail strike had not occurred, see figure 1. The trip continued from SLW to Windsor Airport (YQG), Windsor, Ontario Canada, and then to YIP.  During a maintenance pre-flight inspection at YIP a day after the accident, external damage to the fuselage, missed during the flight crew’s walk-around in SLW, was discovered. Further inspection of the airplane revealed substantial damage to internal structural members of the lower fuselage. Figure 1. Photo of skid assembly on airplane with tailstrike indicator position shown. (Source: Boeing)The tail skid assembly was removed from the airplane and sent to the Boeing equipment quality analysis (EQA) laboratory for examination. No mechanical anomalies were found with the unit Page 3 of 7 DCA23LA232that would have affected the tail bumper strut from properly stroking and rebounding when pressurized and installed on the airplane. Although contamination, metallic and organic, larger than the design specification was found within the unit, it could not be determined how it affected the operation of the unit.