DEARBORN, Mich. - Ford Motor Co. is the most profitable it's been in a decade, since the days when Americans were snapping up SUVs. But maintaining that momentum - and meeting the high expectations of buyers, workers and investors - will be a big challenge in the coming year.

Ford got a taste of that Friday. Despite reporting a profit for 2010, the company's stock fell more than 13 percent to close at $16.27. Investors were disappointed that the results fell short of expectations. Ford also posted an 80-percent drop in fourth-quarter net income, missing forecasts and ending two years of better-than-expected results.

It was clear Ford won't have much room for error as it tackles nagging problems, from the huge loans it took out to fund its turnaround to its upcoming labor talks to its stodgy, slow-selling Lincoln brand.

"When a company consistently beats expectations, analysts and investors start pushing. They raise the bar to the extent that eventually they're going to miss it," Standard and Poor's analyst Efraim Levy said.

Ford earned $6.6 billion, or $1.66 per share, last year, more than double the $2.7 billion, or 86 cents per share, it made in 2009. That was the most it's made since 1999, when it earned $7.2 billion.

But excluding charges from debt reduction and other items, Ford earned $1.91 last year, below the $2.05 analysts expected.

Ford said it should have kept analysts better informed about potential problems in the fourth quarter, including a loss in Europe and a $1 billion increase in costs in North America, partly to fund the launch of new products like the Ford Explorer.

By any measure, Ford has made big improvements since CEO Alan Mulally joined the company in 2006. Using a $23.5 billion loan it got from mortgaging its factories and other assets, including its blue oval logo, Ford sold or shuttered five of its seven brands, closed or sold a quarter of its plants and cut its global work force by more than a third. It also slashed labor and health-care costs, plowing the money back into the design of well-received new products such as the Ford Fusion sedan and Ford Edge crossover.

As a result, a leaner Ford was in a good position to scoop up U.S. market share when its Detroit rivals, General Motors and Chrysler, filed for bankruptcy protection in 2009 and when Toyota announced a damaging series of safety recalls last year. Ford's U.S. sales jumped 20 percent in 2010, double the rate of the rest of the industry. The Ford brand was the top-selling brand in the U.S. last year, besting Chevrolet and Toyota for the first time since 2003.

Ford wants to hang on to those gains, but that won't be easy. While U.S. sales are expected to recover further this year as the economy improves, Ford heads into 2011 with two fewer brands than it had in 2010, after selling Volvo and closing Mercury. Many Mercury buyers will consider Fords, but not all of them. According to Edmunds.com, 37 percent of people trading in a Mercury in December bought a Ford, but 39 percent bought Japanese or Korean brands.

Levy said buyers' memories of GM, Chrysler and Toyota's struggles also are fading.

"Those factors are moving into the rear-view mirror, so the competition is there," he said.

Ford also trails in the luxury segment, where its Lincoln brand has struggled for years with an uncertain identity and dull cars that don't measure up to Cadillac and other rivals. Ford plans to release seven new or revamped Lincolns in the next four years, and it's closing hundreds of Lincoln dealerships in order to make the remaining ones more upscale and profitable. But Mulally says it will be two years before buyers start to see real changes.

Another potential drain on Ford's income could be the United Auto Workers union, which negotiates a new contract with Ford this fall. Ford's U.S. factory workers turned down a 2009 agreement that would have frozen entry-level wages and limited their ability to strike. With an eye on Ford's healthy profits, workers also may demand that the company restore some of the wage cuts they agreed to in their last contract.

Ford made a peace offering to its 40,600 U.S. factory workers Friday, announcing that they would get $5,000 profit-sharing payments this year. It's the first time Ford has handed out the checks since 1999.

Ford's stock recently hit a five-year high of $18.79 after falling as low as $1.43 in 2008, when the future of Ford and its Detroit rivals was uncertain.

Mulally remains upbeat about 2011, saying the company expects profits and cash flow to improve. Chief Financial Officer Lewis Booth said debt reduction efforts also will continue, aiming to get Ford back to investment-grade status. Debt fell from $33.6 billion to $14.5 billion during the year, lowering Ford's interest payments by a little more than $1 billion. A $960 million charge related to debt reduction was one reason for Ford's weak fourth-quarter results.

Booth also cited some important new products coming this year, including the debut of the new Ford Focus in Europe, Asia and North America.

Fitch Ratings, unfazed by Ford's earnings miss, raised the company's corporate debt ratings to "BB," or two notches below investment grade.

Bill Selesky, an analyst with Argus Research, remains bullish on Ford.

"There are too many good things going on at Ford to say that the story's over," he said.