Southwest Airlines Co. slipped to eighth from No. 1 in on-time arrivals the last 23 years, since the federal government began tracking results.

Southwest's on-time performance fell as Philadelphia's second-busiest carrier expanded in congested Northeast air space, including New York LaGuardia and Boston Logan Airports, according to Department of Transportation data. Southwest's policy of not charging for checked bags has kept planes flying fuller.

Southwest was on time 81 percent of the time in the 12 months ended Oct. 31, compared with an average 81.9 percent on-time performance over the last 23 years. Southwest was on time 77.5 percent of the time in October 2010, compared with 84 percent for US Airways Group Inc., and a 95.4 percent timeliness for Hawaiian Airlines, which flies only in warm climates.

Southwest still has the fewest customer complaints among major airlines: 0.22 percent per 100,000 passengers boarding planes in October, compared with 0.28 complaints in October 2009.    - Linda Loyd