Saudi Arabian Airlines flight 919, an ACT Airlines Boeing 747-400F, experienced a tail strike during takeoff from Dammam-King Fahad International Airport. The aircraft initially held a holding pattern to the west of the airport and subsequently diverted to Jeddah. After 17 minutes of holding, the flight crew decided to divert, resulting in landing at Jeddah. Investigation revealed a primary cause of the tail strike was a 100-ton less-than-actual weight entry into the OPT, coupled with a flight crew override of the FMS dashed values.Saudi Arabian Airlines flight 919, an ACT Airlines Boeing 747-400F, experienced a tail strike during takeoff from Dammam-King Fahad International Airport. The aircraft initially held a holding pattern to the west of the airport and subsequently diverted to Jeddah. After 17 minutes of holding, the flight crew decided to divert, resulting in landing at Jeddah. Investigation revealed a primary cause of the tail strike was a 100-ton less-than-actual weight entry into the OPT, coupled with a flight crew override of the FMS dashed values.