Desperate to sell seats on increasingly empty jetliners, airlines are slashing airfares to prime overseas destinations in Europe and Australia.

The blue-light specials for international travel are broad and, in a break from recent years, touch tourist hot spots like London and Paris for summer flights that usually sell out early and command top dollar.

It's a sign that the swift, troubling plunge in demand for international air travel that began last fall is worsening and extending through the peak summer travel months, when airlines historically have garnered the bulk of their profits.

"We're seeing a major distressed airfare sale," said Tom Parsons, editor and founder of BestFares.com. "It's definitely a flier's market."

Bargain hunters can travel from Chicago to Sydney for $947 in July, 57 percent less than they would have paid a year ago, according to BestFares.com. An economy seat to London is available for $802, including fees, down 36 percent from 2008 rates, while airfare to Paris has been slashed 43 percent.

Prices are even lower for consumers with the means and flexibility to hit the skies this month. A host of carriers are offering round-trip tickets from Newark, N.J., to London for less than $90, although costs total $450 when taxes and fuel charges are included, according to Vayama.com. Other steals include Los Angeles to Munich, Germany, for a total of $568, and Miami to Lima, Peru, for $411.

While such deals may be alluring to consumers, industry watchers worry the deep discounts pose a new financial threat to the perpetually ailing U.S. airline industry, especially since international travel has been a major contributor to their profits over the past five years.

"This is unprecedented," said Jean Covelli, president of The Travel Team Inc., a wholly owned subsidiary of Buffalo-based conglomerate Rich Products Corp.

"I think we might be seeing a forever-changed industry when we come out on the other side of this in terms of mergers, consolidation, frequencies and the routing of flights, with perhaps a number of cities being cut out of air service."

Airlines are being hurt by a falloff in international traffic and fewer numbers of corporate travelers paying premiums to purchase business- or first-class seats. Los Angeles aerospace executive Tom Lee, who normally hops the globe several times a month visiting suppliers and customers, hasn't ventured overseas since December.

"There is a sense at the moment that only critical travel should take place," Lee said. "In other words, courtesy travel and routine, non-essential meetings of the past are curtailed just because of the pervasive sense of global economic conditions."

Most major U.S. carriers had looked to international travel to prop up sagging domestic results. Led by Delta Air Lines and United Airlines, they shifted Boeing 757s and 767s from domestic flying to trans-Atlantic and Latin American routes to take advantage of the global economic boom that peaked in 2007.

But that strategy isn't paying dividends in recessionary times, and carriers soon will have to decide whether to scale back their global ambitions.

"I think it will be ugly," said Hubert Horan, an aviation consultant who previously headed international planning for Northwest Airlines and who thinks a major restructuring is inevitable.

"No one could have foreseen a year ago or three years ago that we'd see this level of demand decline, but they put themselves in a bad situation by overexpanding," Horan said.

United's international revenue passenger miles, a measure of miles flown per paying customer, declined 22 percent in February. American Airlines saw a 13 percent drop for the month.

Both carriers have trimmed international capacity, and a United spokeswoman said the Chicago-based carrier is open to making deeper cuts, if need be.

But a host of factors make it difficult to pull back overseas flying. U.S. airlines are locked into schedules created months ago, and they risk losing landing slots worth millions of dollars in capacity-constrained European airports such as London Heathrow and Frankfurt, Germany, with "use it or lose it" policies.

"You can't turn a schedule on and off," said Mary Frances Fagan, spokeswoman for American. "Just because international traffic seems to have taken a hit, we can't say we aren't going to make those flights tomorrow."