Heilman is now the second-fastest 15-year-old in U.S. history after clocking 1:58.01, trailing only Phelps, who set the world record in 1:54.92 at that age.
Caeleb Dressel is the favorite in the men's 100 fly, though he has been beaten twice this year in the race: once by Michael Andrew and once by Shaine Casas.