After avoiding New York City's large airports for years, Southwest will begin serving LaGuardia (from Gate B4 in its central terminal) on June 28 with five daily nonstop flights to Chicago Midway (starting at $178 roundtrip) and three daily flights to Baltimore Washington International airport (starting at $98 roundtrip). Connecting service to Denver, Las Vegas, San Diego, Seattle, and L.A. will also be offered, says the airline. Tickets are now for sale.

Up until now, Southwest's closest gateway in New York City was Long Island's Islip.

Everyone will be watching if Southwest experiences severe delays at the notoriously traffic-plagued LaGuardia, causing a ripple effect throughout its national system. Perhaps Southwest will do a better job of handling delays and their effects on air traffic control nationwide than other airlines have.

In other expansion news, the airline is also starting flights at Boston's Logan International Airport in the autumn.

Aviation consultant Stuart Klaskin has recently speculated that Southwest might start flying "shuttle" service between Boston, New York City, and Washington, D.C.—a market currently dominated by Delta and US Airways with a typical $600 round-trip fare.

The new service between LaGuardia and Midway is direct challenge to American Airlines and United Airlines, which thought they had that route "locked up."

In other changes, Southwest plans to revamp its frequent flier program, which rewards customers with a free trips after about eight roundtrip flights. Ms. Wright says the revamp is expected late this year or early in 2010.