U.S. airlines are ending a prolonged period of cutting back their flying capacity on domestic routes.
For travelers, the growth in the supply of airline seats could lead to relief from rising airfares.
Fliers could also find more elbow room on crowded flights.
"It could spell a little bit of relief," says consultant David Beckerman of Back Aviation Solutions.
According to a USA TODAY analysis, airlines, including regional partners, will increase their domestic seat offerings by nearly 2% in November 2006 compared with November 2005.
Annual growth for December will be about 3% from a year earlier. It will be the first time since summer 2005 that U.S. airlines have increased domestic capacity on a year-over-year basis.
The calculation varies among airlines, but decisions to add seats generally reflect greater optimism in the industry about its prospects for making money.
"When you see the kinds of demand we're experiencing, the only conclusion you can reach is that the market wants more of our service," says David Messing, a Continental Airlines spokesman.
Continental is the only network carrier that has increased domestic capacity every month this year compared with last year, the analysis shows.
Discounters are the main source of the increased capacity. Southwest, JetBlue and AirTran added most of the net new seats for December. As of December, low-cost carriers will fly one out of every four seats in the USA.
John Heimlich, economist at the Air Transport Association, says strong demand and 14 consecutive months of year-over-year revenue gains for airlines will make some carriers "bullish" about capacity.
Not every airline is as optimistic. No. 1 American, for example, has scheduled slightly fewer seats for November and December compared with a year earlier.
Aviation consultant Robert Mann says airlines are taking some risk if they continue to grow capacity when the economy could be cooling.
"It may turn out that people are putting capacity back at exactly the time where it's no longer supportable by underlying economic growth," Mann says.
If so, the added seats would translate to moderation in recent fare increases and fewer fully packed flights.
