Fifteen-year-old South Shore resident Grant Swift can’t quite pinpoint the moment flight first grabbed his interest.But now that the love of being airborne has taken hold, it appears unlikely to let go.“He doesn’t want to slow down when he has a goal,” said Russell Holtz, chief flight instructor at SoaringNV in Minden, who has flown with Swift dozens of times in the past couple years as part of the teenager’s push toward a license to glide.Despite the aerial maneuvers Holtz and Swift have performed in the skies above Lake Tahoe, it was the first time Holtz didn’t fly with Swift …