Alcoa Inc , the largest U.S. aluminum producer, posted a stronger-than-expected second-quarter profit on Monday and raised its estimate for global aluminum consumption, sending its shares up 3 percent.

The company, whose results are often viewed as a bellwether of the U.S. economy, cited strength in several industrial sectors -- particularly in packaging, commercial transportation and building and construction. It also raised its estimate for aluminum consumption this year, even as metal prices have been falling recently.

Chairman and Chief Executive Klaus Kleinfeld told Wall Street analysts that strong industry fundamentals were expected to drive demand for aluminum in the next ten years with an average growth rate of 6 percent per year.

You see robust consumption growth in places like China, Brazil, India, modest increases in North America and Europe.

There's a lot of very positive indications there of a real recovery in almost all of these markets, he said on a conference call. But I believe that the biggest risk is still the volatility that could potentially come from financial markets.

Asked about Alcoa's mid- to long-term strategy, Kleinfeld said: Obviously, we will continue to do cost-cutting, obviously, we will continue to see end-markets picking up.

We will have a seasonal decline ... like we currently see in Europe, for instance. (But) order books -- even in Europe, look very good.

Based on the improved end-market demand, Kleinfeld said Alcoa was raising its projection for global aluminum consumption from 10 percent to 12 percent this year.

In another sign of growing optimism about the economy, U.S. railroad CSX Corp posted a 36-percent rise in second-quarter profit, citing sharp jumps in shipments of cars and metals.

In its earnings release, Alcoa said net profit was $136 million, or 13 cents per share, compared with a loss of $454 million, or 47 cents per share in the same quarter last year. Earnings from continuing operations were $137 million, 13 cents per share.

Revenue rose 22 percent to $5.2 billion, the Pittsburgh-based company said.

Analysts on average were expecting earnings of 11 cents per share and revenue of $5.047 billion, according to Thomson Reuters I/B/E/S. Please see:

It's constructive and it helps start the earnings season off on a positive note, said Brian Hicks, portfolio manager of U.S. Global Investors in San Antonio, Texas.

From the standpoint of Alcoa, they see the economy continuing to expand. It's robust enough that they have to increase their forecast for global aluminum production.

During the quarter, Alcoa said there was a 1-percent increase in third-party prices for alumina -- the raw material for aluminum. However, that was offset by a 1-percent decrease in realized prices for the metal.

In the past three months, the price of aluminum in London has dropped sharply, from over $2,400 per tonne in April to around $2,000 as weak demand for cars, planes and construction and uncertainty over the strength of the global recovery have weighed on the metal.

Alcoa shares rose to $11.24 in extended trade after closing at $10.87 in the regular session on the New York Stock Exchange.

(Reporting by Steve James, editing by Bernard Orr.)