With a prominent new billboard on U.S. Interstate 26 and a flurry of online fare sales, the countdown begins for Southwest Airlines' local service launch on March 13.

Special offers that began this week include rates starting at $59 for a one-way flight to Nashville, $79 to Baltimore and $99 to Chicago on the discount carrier's website. Southwest spokeswoman Ashley Dillon said Charleston residents can expect more of that in print, radio and television advertising ahead of the inaugural flight.

"You'll definitely start seeing more of Southwest over the next two months," Dillon said.

Just days before the first flights take off from Charleston International, Southwest also begins the revised version of its frequent-flier program called Rapid Rewards. Dillon said the new points-based system could attract new members -- including more high-spending business travelers -- and generate several hundred million dollars in revenue for the Dallas-based company during the next few years.

For nearly 25 years Southwest has used a program that gives a passenger a free standard flight after eight round-trip flights, or 16 trips total, made within a two-year period. Travelers earn more when they fly business class and double when they fly 750 miles or farther at that higher rate.

Now passengers earn 12 points for every dollar spent on a business flight, 10 points per dollar on every standard flight and six points per dollar on every deeply discounted "Wanna Get Away" flight. When cashing in, a $1 credit can be redeemed for every 60, 100 or 120 points, depending on the type of fare.

Unlike the current Rapid Rewards, Southwest won't impose "blackout days" when members can't use their credits. Plus, the points don't expire after two years.

Although the new program raises the question of whether customers who pay higher rates benefit more, Dillon pointed out that in the past Rapid Rewards captured a relatively small number of participants, considering the airline's share of the market.

"We should have more Rapid Rewards program members than we do," Dillon said. "We think it's going to help us capture some of those people."

Tim Winship, an airline-industry veteran who edits FrequentFlier.com, said Southwest's changes were long overdue.

"Their program has been a laggard for years," Winship said. "This is head-and-shoulders above the old program, and my guess is it's going to stack up pretty well against programs of legacy carriers" such as American, Delta and United.

He noted that Southwest is still viewed dimly by many business travelers because it does not offer first-class cabins or airport lounges.

The Associated Press contributed to this report. Reach Allyson Bird at 937-5594.