AIR FARES FOR BUSINESS SOARING HIGH.

Byline: Adam Bryant The New York Times

Need to fly from New York to Los Angeles at the last minute? It will cost you $1,748 for a midweek round trip. From New York to Dallas? $1,508 round trip. How about Atlanta? The fare is $1,046.

Since the summer of 1992, when a bruising fare war sent tens of thousands on whimsical trips, airlines have been steadily raising ticket prices for travelers, typically business people, who fly during the workweek on short notice. The increases have hit particularly hard for smaller companies that lack the clout to negotiate discounts with airlines.

The average round-trip business fare climbed to $820 in January from $442 in May 1992, an 86 percent jump, according to American Express Travel, which compiles an index of typical business fares. Over the last year alone, the fares have gone up 28 percent, and just March 7, airlines raised fares an average of 4 percent.

``The fares are at historical highs,'' said Eric Altschul, vice president for the consulting services group at American Express Travel. ``I don't see anything that is going to change this in the near future.''

For leisure travelers, fares are also up, but for the most part only slightly. Leisure fares tend to change rapidly based on the time of year and destination. And rock-bottom deals are still available, particularly through fare sales distributed over the Internet for weekend trips.

But leisure fares are only available for a limited number of seats on some flights and often must be purchased several days or weeks in advance.

As such, fare sales do little good for people like Richard Hill, executive vice president of Biach Industries in Cranford, N.J., a company with 30 employees that supplies hydraulic systems to nuclear plants. Hill, who oversees Biach's travel budget, said that when a Biach employee had to travel recently on short notice to Charlotte, N.C., there was no way to avoid the fare of about $800 that the company was quoted - except to drive, which his colleague decided to do.

``For a small business, it's very tough,'' Hill said. ``The fares are outrageous.''

Airlines have been raising fares for a simple reason: Travelers have shown they are willing to pay them. After all, the U.S. economy is healthy, generating new demand for air travel.

The airline industry has also learned an important lesson in recent years. As a rule, airlines have generally responded to stronger passenger traffic by operating too many planes, which led to fare wars as they fought to fill seats at the expense of competitors.

But now, after billions of dollars in losses in the early 1990s, airlines are collectively keeping tight control on the number of seats they sell. That gives them greater control in setting fares, particularly for those passengers who have no choice but to accept the fare they are quoted.

Airlines are also making greater use of sophisticated computer software to help them set fares on individual routes based on past booking patterns.

All this is good news for investors in airlines, however. The industry is generating record profits - $3.2 billion last year, according to the Air Transport Association, an industry trade group. And many industry experts say this year will be even better.