Phelps finished in 51.04 seconds at the Mutual of Omaha Swimvitational, beating world record-holder Ian Crocker's previous 2008 best of 51.32, which Crocker recorded in Austin, Texas, in March.
"I really wanted to break 51 in the 100 fly, but my finish kind of wasn't too good," Phelps said. "I kind of kissed the wall. It's really not how you're supposed to finish. Hopefully it's something I can work on in the next two weeks."
Phelps, who was 0.64 seconds off Crocker's world record of 50.40, said he might have gone under 51 if he had glided into the wall rather than taking a half-stroke at the finish.
"It's all a learning experience," he said. "I'd rather have it here than in the next two months."
Phelps won the 100 butterfly at the 2004 Olympics — one of his six gold medals in Athens — and he's on track to meet Crocker here in three weeks at the U.S. Olympic trials.
"I always look forward to racing him," Phelps said. "In this pool, we're both hopefully going to be on our best and ready to race."
Phelps said he likes the Qwest Center's arena environment and the temporary pool.
"Just walking on the pool deck makes you excited," he said. "It's definitely a good warm-up for the trials."
Phelps also won the 100 freestyle at the meet Friday in 49.53, a time he called disappointing.
He's scheduled to swim the 200 freestyle and 100 backstroke here on Saturday. He left open the possibility of skipping the finals of the 200 free to concentrate on the 100 backstroke at night.
After his fast 100 butterfly, Phelps faced continued questions about his swim apparel — the Speedo LZR Racer. Though world governing body FINA has upheld the legality of Speedo's design, the suit has been one of the hot-button issues in swimming. Since mid-February, swimmers wearing the suit have set 37 world records.
Phelps shrugged off questions about the suit.
"Anybody in the world can wear one. If you want a suit, you can get one if you want. They're available to everybody," he said. "The suit is definitely a help. Without the training, nothing else happens. The suit is helpful for hundredths or tenths of a second, to do a best time or win a gold medal. Hopefully, that's what we'll be able to use it for."
Peter Vanderkaay made a good run at breaking his American record of 3:43.82 in the 400 freestyle.
Vanderkaay, who swims for Club Wolverine, was .23 seconds off his record pace going into the final 100 meters, prompting the 5,100 fans to get on their feet and urge him on the rest of the way. But Vanderkaay said he tired the last 50, and he was timed in 3:45.60.
"I was trying to go as fast as I could, and I'm happy with that swim," he said. "Once you hit this level, you always think about world records and fastest swims. Right now I'm concerned about doing what I have to do to make the (Olympic) team, and the times will take care of themselves."
Eric Shanteau won the 200 breaststroke in 2:12.18.
Kate Ziegler followed her Thursday win in the 1,500 freestyle with an easy victory in the 400 free. She was timed in 4:07.1, more than 3 seconds ahead of Allison Schmitt.
Katie Hoff, the American record-holder in the 400 free, passed on the event but will compete against Ziegler here in three weeks at the trials.
Agata Korc of Poland won the women's 100 freestyle in 55.21 and Rachel Komisarz won the 100 butterfly in 58.73.
Caitlin Leverenz won the 200 breaststroke in 2:26.00, holding off a hard-charging Hoff. Olympic champion Amanda Beard was disqualified in the prelims because of a flaw in her technique. USA Swimming spokeswoman Karen Linhart said officials ruled Beard's elbows were not underwater during the recovery portion of the stroke.
Beard later failed to reach the finals in the 100 butterfly, an off event for her. She came nearly a full second short of the cut line for the trials.
Source : AP