Fleetwood fired the 63 at the Kingsbarns course in joining Michael Hoey atop the leader board at 12-under 132. Hoey, who also played Kingsbarns Friday, shot 6-under 66 in his second round.
Louis Oosthuizen, who was one of three golfers tied with Hoey in first after Thursday's play, was 5-under Friday and is alone in third at 11-under. Five players, including first-round co-leader Markus Brier, are another stroke back at 10-under.
The tournament is contested over St. Andrew's Old Course, Carnoustie and Kingsbarns, with each golfer playing each course over the first three rounds. Sunday's final round is played on the Old Course.
Fleetwood, who has Carnoustie to face Saturday, blistered Kingsbarns with four birdies in his first six holes. He added another at No. 9 and came in with another four in a six-hole span from Nos. 12-17.
Hoey had just one bogey and that came on his second hole. His seventh birdie on the day came at No. 18.