Deflation has become a central  concern these days. The Federal Reserve sweats the notion of falling prices across the economy, as it tends shrink asset values even as debts against those assets remain constant. And companies hate deflation, because it usually signals weakening revenue, margins and profits. For many firms, it’s simply impossible to even think about raising prices. But in a few industries, pricing power has come back, and investors may be underestimating the future earnings power that can result.

Fewer planes means more pricing power
When the airlines experienced the turbulence of 2008, they took a lot of planes out of commission. And as soon as the economy rebounded and demand for air travel started to build, many assumed that the airlines would simply bring all those mothballed planes back on line. It hasn’t happened. Instead, airlines saw this as an opportunity to not shoot themselves in the foot, which they had done every time before.

A quick glance at Delta‘s (NYSE: DAL) recent quarterly results spells out the benefits of restrained capacity. The nation’s largest carrier boosted the number of planes in service by 2%, but demand was more robust than last summer, helping Delta to boost revenue per passenger from $12.22 per mile flown to $14.22 — a +16% jump.

The payoff: Analysts at Bank of America note that the publicly-traded U.S.-based airlines likely earned a record $2.4 billion in the third quarter, up from a $260 million loss last year. Industry laggard AMR (NYSE: AMR) even managed to post its first quarterly profit in two years thanks to surging yields and slower-to-rise costs.

Industry watchers expect airline carriers to only slowly add more planes back into the service, below the rate that would lead to price wars. American Express just issued a report predicting that tight supply will enable airfares to rise another +2% to +6% in the United States next year, and +5% to +10% in the rest of the world. That’s a real positive for Delta, AMR and United Continental (NYSE: UAL), as these carriers are most heavily exposed to international travel. The weak dollar may impede some Americans from traveling abroad, but could trigger a fresh surge of foreign tourism to the U.S.

Fewer discounts mean higher prices
Auto makers are also benefiting from restrained supply to help firm prices. Advertised prices for new cars and trucks are rising only modestly, but auto makers are finally able to stop the rebate game, which often took $1,000 to $2,000 off of the listed price. They can afford to do that since many auto plants were shuttered during the downturn, and few will be re-opened. Domestic auto plants are now producing two million fewer cars than a few years ago, and similar cutbacks have been made in Europe.

Even as industry sales still remain in a funk, pricing power is already in evidence. Goldman Sachs expects U.S. auto and truck sales to be around 11.5 million this year, well below the 17 million unit levels seen back in 2006 and 2007. Yet they expect that figure to rebound to 13 million next year, 14 million in 2012 and 15 million in 2013. As long as the auto makers expand output at levels in line or below industry sales, they should see continued improvements in pricing power.

As an example, Ford Motor (NYSE: F) has produced about -10% fewer vehicles in the third quarter than the second quarter. That means fewer cars will pile up on dealers’ lots, and Ford will not need to resort to profit-sapping rebates to move the metal. We’re typically bombarded with year-end closeout specials from car dealers in September and October, but that’s not happening as much this time around, as inventories remain quite lean.

Reversing the freight pricing trend
When economic activity slowed, major publicly-traded trucking firms such as Arkansas Best, Con-Way, J.B. Hunt, Knight Transportation, and Heartland Express had to take a number of trucks out of service. Nowadays, demand for freight carriers is increasing, and thanks to better control of supply, these firms are finally able to push through some badly-needed price increases. As Dahlman Rose’s Jason Seidl recently wrote, “the industry, whose recovery has lagged that of other modes of transportation, is experiencing a gradual return of pricing power, resulting from dwindling capacity and improved demand.”

As this is a business with high fixed costs, moderate revenue growth can lead to much faster profit growth. For example, J.B. Hunt (Nasdaq: JBHT) is expected to boost sales +12% next year (half from volume increases, half from price increases), though per share profits are expected to rise +28%. Arkansas Best (Nasdaq: ABFS) is expected to swing from a $1.31 a share loss in 2010 to a $0.67 per share profit next year.

Alcoa’s upturn
Sometimes, an industry giant can set the tone for a whole industry. Alcoa (NYSE: AA), one of the world’s largest aluminum producers, has severely reduced output, and management insists that the company will be slow to rebuild output when the industry rebounds. It helps that Chinese aluminum producers are cutting output. I discussed Alcoa’s newfound discipline in this recent article.

Alcoa’s management discussed the improving industry dynamics in great detail on its recent conference call. Other industry players such as Century Aluminum (Nasdaq: CENX) stand to benefit from Alcoa’s leadership on the supply front. Then again, that’s bad news for companies like Noranda Aluminum (NYSE: NOR) and Kaiser Aluminum (Nasdaq: KASU), which count on cheap prices to boost their profit margins on manufactured aluminum goods.

Action to Take –> Many of these supply-induced pricing gains are impressive enough in a weak economy. They’ll look even more impressive when the economy rebounds, as long as supply growth lags demand growth. These sectors have already posted decent gains, but investors are likely under-estimating their impressive earnings power when the economy is back in growth mode.

Of the companies mentioned here, Ford Motor, Aloca, AMR (because it’s much cheaper than the other airline stocks) and Arkansas Best are my favorite names to consider.