ST. GEORGE - SkyWest Airlines, a Delta Connection carrier, reported its May revenue passenger miles rose 26.9 percent to 15.3 million over the 12.1 million reported in May 1987.

For the third straight month the rising RPMs outdistanced available seat miles and boosted the load factor to 42.5 percent. The airline carried 78,375 passengers in May.

Commenting on the airline's strong showing, Steven Hart, market analyst, said, "May's statistics reflect the longer stage lengths we have integrated into the schedule, but more importantly the numbers show the growing popularity of our service in new markets."

SkyWest recently inaugurated service to Great Falls and Kalispell, Mont. and Casper, Wyo. The airline plans to initiate nonstop Orange County to Salt Lake City service July 1.