Pittsburgh International Airport will be adding 700 parking spaces between now and Thanksgiving, a move officials tied to growing demand spawned by lower fares, more competition and the arrival of low-fare heavyweight Southwest Airlines.

The new spaces will supplement 400 the Allegheny County Airport Authority opened to the public in April by reallocating them from the employee parking lot.

Those spaces were added to the extended term parking lot, as the 700 new ones will be. The extended term lot is the one farthest from the terminal.

With the additions, the extended term parking lot will have 8,200 spaces by Thanksgiving, by far the most at the airport. The long-term lot has 2,400 spaces and the short-term garage has 2,100 spaces.

In March, the airport authority increased the extended term daily rate from $5.75 to $6.50.

The Airport Authority is freeing up land for the spaces as part of a $4.5 million reconstruction of Return to Terminal Road, which allows those motorists heading out of the airport to circle back toward the terminal building.

Authority spokeswoman JoAnn Jenny said the road, now a straightaway, will be arched and pushed back to provide more room for parking. A second lane also will be added and intersection improvements will be made. A gas line also will be relocated.

The decision to add spaces coincides with increases in parking and parking revenue. For 2004, the number of vehicles parked jumped by 6 percent over 2003 and revenues rose by 8 percent. For 2005, as of the end of April, the number of vehicles parked was up another 1.5 percent and revenues were up 7.8 percent.

Jenny and authority Executive Director Kent George attributed the greater demand to an increase in local traffic spawned by lower fares and more competition resulting from the decision by US Airways to drop Pittsburgh as a hub last November.

In fact, despite repeated cutbacks by US Airways, still the airport's dominant carrier, local traffic -- at 3.75 million travelers -- reached an all-time high last year.

George said the authority is expecting even more local traffic, meaning those beginning their trips at the airport, in 2005 because of the May 4 start of service by Southwest Airlines, with its legendary ability to stimulate the local market and to expand the reach of the airports it serves.

"We've been seeing higher [local traffic] on all the airlines," Jenny said. "A lot of carriers are offering more discounts. The regional traffic is going up because there's more competition. The air fares have gone down since US Airways isn't operating a hub out of here."