American Airlines flight 1586, a Boeing 737-800, experienced a tailstrike upon takeoff from runway 7L at Los Angeles International Airport, California, USA. No injuries occurred during the event. The flight landed uneventfully at Toronto-Lester Pearson International Airport, Canada, where damage to the tail skid was discovered. Further damage to the aft pressure bulkhead was later discovered, and this damage was determined to be substantial. According to the captain, normal procedures were followed during preflight and taxi, including verification of the takeoff bug speeds. During the takeoff roll, the automatic, aircraft-generated V1 callout occurred and he began to rotate the airplane. The first officer did not call for rotation at that time. The captain applied nose up pitch command until he realized the indicated airspeed was too low. He said he then eased the nose of the airplane back down to the runway and re-rotated at the normal rotation speed, achieving approximately 10 degrees nose up at about 155 to 160 knots. The FO said he noticed that the automatic voice callout occurred about 20 knots early and observed the captain rotate for takeoff, but he said nothing to the captain for fear of causing confusion. The rest of the climbout, cruise, descent, and landing at Toronto was uneventful. According to the first officer, during preflight preparations, due to a last minute runway change, the takeoff data V speeds did not automatically upload into the flight management computer (FMC), so he manually entered the speeds using information on the preflight paperwork. Flight planning data indicated that the airplane takeoff weight was 161,037 pounds with a center of gravity at 22.5% mean aerodynamic chord, which under the conditions at the time of the accident should have resulted in a flaps 1 takeoff with V1 (takeoff decision speed) of 153 knots, a Vr (rotation speed) also of 153 knots, and V2 (scheduled takeoff speed) of 158 knots. The recorded data indicates the manually entered V speeds in the FMC were V1 123 knots, Vr 153 knots and V2 158 knots. Probable cause: The early rotation of the airplane to an angle at which the fuselage contacted the runway. Contributing to early rotation was the Captain’s reaction to the erroneous V1 automated callout, likely assuming that the airplane was at or close to the correct Vr at the same time. The erroneous automated callout was likely due to a keystroke entry error by the FO when manually entering takeoff data for a newly assigned departure runway.