It was just a matter of time before the March 24 Dubai World Cup (UAE-I) and the other races that day at Nad Al Sheba came in to play on the 2001 leading sires list. Four of the six stakes were won by offspring whose sires stand in North America, and it was Fly So Free's son Captain Steve who won the $6 million Dubai World Cup and earned $3.6 million in the process. Fly So Free, who took over the top spot on the sire list from Cee's Tizzy (now fourth), has progeny earnings of $4,197,792. A son of Time for a Change out of the Stevward mare Free to Fly, Fly So Free stands at Robert N. Clay's Three Chimneys Farm near Midway, Ky.The other three North American stallions with added-money winners that March 24 afternoon in Dubai moved up to the top six after not having been ranked among the top 70 sires the previous week. Phone Trick, whose son Caller One earned $1.2 million in winning the Dubai Golden Shaheen (UAE-III), ranks second, with $1,740,821. Phone Trick (Clever Trick -- Over the Phone, by Finnegan) stands at John T.L. Jones' Walmac International near Lexington.Florida stallion Tour d'Or holds down the No. 3 spot, with $1,668,855. His son, Express Tour, won the UAE Derby (UAE-III), earning $1.2 million. Tour d'Or (Medaille d'Or -- Debby's Turn, by Turn to Mars) stands at P. Noel Hickey's Irish Acres Farm near Ocala.A.P. Indy (Seattle Slew -- Weekend Surprise, by Secretariat) moved up to sixth-place after the $600,000 earned by his son Festival of Light in winning the Godolphin Mile (UAE-III) was included in his progeny earnings. A.P. Indy, whose runners have earned $1,212,022, stands at William S. Farish's Lane's End Farm near Versailles, Ky.