The U.S. women beat Australia in a 4x100m freestyle relay for the first time in nine years, while Kate Douglass led off by missing the 100m free world record by one hundredth of a second.
Kate Douglass, Gretchen Walsh, Torri Huske and Simone Manuel combined to swim 3:29.32, an American record and the third-fastest time in history.
Douglass' leadoff time — 51.69 seconds — was also an American record and one hundredth off Dutchwoman Marrit Steenbergen's world record.
The U.S. last beat Australia in a women's 4x100m free at the 2017 World Championships. Australia won the last four Olympic titles, plus four of the last five world titles.
Pan Pacs, which are for swimmers outside Europe, conclude Saturday with preliminary heats at 1 p.m. ET and finals at 10 p.m., live on Peacock and NBCSN.
Also Friday, Australian Lani Pallister notched her first career win over Katie Ledecky, taking the 400m freestyle in a personal best 3:58.42. Ledecky was runner-up in 4:00.15.
Canadian Summer McIntosh, the world record holder, won the B final in 4:00.58 after placing ninth over the preliminary heats.
Pallister and Ledecky are expected to go head-to-head again Saturday in the 800m free, an event Ledecky has never lost at a major meet.
At last summer's World Championships, Pallister came closer to Ledecky than any woman ever in a championship 800m free, touching 36 hundredths behind.
Australian Lani Pallister led for most of the race and held off Katie Ledecky to win the 400m freestyle final at the Pan Pacific Championships.
Walsh swam the 100m butterfly prelims and finals in times (55.28, 55.15) that only she has ever beaten. She now owns the 18 fastest times in history, including the world record of 54.33.
American Gretchen Walsh set a new championship record in the women's 100m butterfly on Day 3 of the Pan Pacific Championships.
In the women's 200 backstroke, Regan Smith earned her first individual title at a major international meet since the 2022 Worlds.
Smith earned silver in the previous 10 backstroke races among the 2023 Worlds, 2024 Olympics, 2025 Worlds and these Pan Pacs (behind fellow American Katharine Berkoff in the 50m and 100m).
Australian Sam Short won the men's 400m free in 3:40.52, the eighth-fastest time in history. Aaron Shackell was third in 3:43.44, a personal best by 1.59 seconds to become the fifth-fastest American in history.