Delta Air Lines Inc. (DAL), the nation's third largest airline, said Thursday it is raising the cap on its most expensive fares by $100 because of persistently high fuel costs. The move comes six months after it announced a ticket price overhaul designed to draw in more business travelers. Its shares surged more than 11 percent.

The Atlanta-based airline said that effective immediately, one-way walk-up fares are capped at $599, up from $499, for economy class and at $699 for first class.

Delta said that it will continue to offer the fares without a Saturday-night stay-over requirement. It also is keeping its reduction of most special service fees to $50 and 1,000 bonus miles for tickets purchased on the company's Web site.

The cap adjustment affects only full-fare walk-up and some three-day advance purchases.

"When Delta launched SimpliFares (search) in January, crude oil was selling at $43 per barrel compared to as much as $61 per barrel in recent weeks," said Paul Matsen, Delta's chief marketing officer. "Despite our best intentions to keep the current fare caps in place, we have been forced to find ways to offset this dramatic spike in costs."

Following the launch of Delta's price program in January, other major carriers followed suit, lowering their most expensive fares as well.

Delta has been trying to cut costs to avoid bankruptcy, but high fuel costs have caused its losses to continue to mount.

Delta shares jumped 38 cents, or 11.2 percent, to $3.78 on the New York Stock Exchange (search). Its shares have traded in a range of $2.46 to $8.17 over the past 52 weeks.