They’ll Take Manhattan, Over Milan or Paris : American designers jump a step ahead of Europe with first fall previews.

American fashion is heeding an age-old principle of business: Get there first.

Just as consumers are beginning to buy spring clothes, the fashion industry has already turned to fall. This week in New York, fashion designers, editors, store buyers and groupies alike are gathering to preview cold-weather clothes that will be in stores months from now. While they’re at it, they’ll make a little fashion history.

For the first time, New York’s designers en masse are upstaging their European counterparts by skipping ahead of shows in London, Milan, Italy, and Paris, which traditionally are held in March.

The scheduling change ironically was prompted by a European designer--Helmut Lang. Shortly after he moved to New York last year, he decided to hold his show in September, two weeks ahead of Europe’s shows. About a dozen American designers followed his lead. Based on their success, 7th on Sixth, which organizes New York’s fashion week, decided to skip ahead this season and has indicated the change is permanent.

Another first happens this week--American menswear and women’s wear designers are combining their market weeks into one long, action-packed presentation. In nine days ending Feb. 19, more than 160 fashion shows and special events will have taken place under tents erected in Bryant Park, crowded showrooms, art galleries and even Grand Central Station.

The move isn’t just about patriotic pride. It’s a calculated effort to boost the profile--and profits--of the U.S. fashion industry. Earlier shows move up production schedules for designers, which ultimately will give consumers a longer shopping season.

“Now the U.S. will be first, rather than last, to place fabric orders, which means clothes will be in the stores sooner,” said Los Angeles designer Richard Tyler, who shows in New York.

New York’s fashion week began Thursday with menswear presentations from the likes of Wilke Rodriguez, Sandy Dalal and Kenneth Cole (who is collecting donated shoes in a special bag to give to the needy). By Sunday, designers such as Cynthia Rowley and DKNY will have coed runways. The combined collections allow designers to present a more cohesive image and save runway show costs. For Maurice Malone and Pelle Pelle, the savings allow them to launch new women’s collections. For others, coed shows help highlight the intersection of men’s and women’s fashion.

American designers hope the move will help their bottom line by capturing a greater share of store buying dollars that might otherwise be spent in Europe.

Under 7th on Sixth, more than 75 American designers are moving their shows from balmy April to chilly February in hopes of cementing American fashion’s trendsetting credentials.

American designers have long been accused of merely reinterpreting trends that appeared on European runways. Showing before the Europeans do sidesteps that issue, said Fern Mallis, executive director of 7th on Sixth.

Enhancing credibility was “. . . a big decision in moving the collections forward,” she said. “They will have to be reviewed without comparison to what people have seen everywhere else.”

The earlier dates proved attractive to a number of European designers such as Britishers Tomasz Starzewski (who is launching a new men’s collection), Philip Treacy and Nicole Farhi; Italian Enrico Coveri; and Custo Barcelona, the Spanish shirt maker.

In the past, New York was simply overshadowed by the enormousness of Europe’s long fashion season.

“Everyone is going to see the New York shows without being exhausted,” Mallis said. “They are coming here without that sense of ‘seen it, done it, surprise me.’ ”

Tyler agrees.

“The press and retailers will see us before the Europeans,” he said, “while they are still fresh.”