Allegiant

Allegiant Travel Co., which operates the airline Allegiant Air, said Wednesday that its passenger traffic soared more than 20 percent in May as it significantly expanded its service.   Allegiant, which specializes in carrying people from smaller cities to resort destinations, said it flew paying passengers 494.9 million miles last month, up 20.4 percent from a year earlier.

The carrier's total capacity, or number of available seats, rose 21.4 percent from a year earlier. Because it added seats faster than it added passengers, its flights were slightly less full. Allegiant's occupancy rate fell 0.8 percentage points to 87.3 percent.

Allegiant estimates that passenger revenue per available seat mile fell between 10.4 and 10.8 percent last month. That metric, a key measure of an airline's financial health, is how much a carrier makes flying one paying passenger a single mile.

Allegiant Travel shares rose 50 cents to $62.96 in morning trading Wednesday. Its shares peaked for the past year at $65.14 per share late May. They traded as low as $40.31 in early August 2011.