* Airlines face massive tangle after flight cancellations
* Retailers resilient in January despite snow storms
* Plains wheat crop faces damage from bitter cold (Adds retail sales, flight cancellations, economic impact)
By Ros Krasny
BOSTON, Feb 3 (Reuters) - Cities across the United States dug out on Thursday from a snow and ice storm that stretched for thousands of miles (km) as air travel remained a mess and local officials struggled to make roads passable.
Many areas grappled with treacherous road conditions after the storm cut a swathe from New Mexico to Maine on Wednesday, paralyzing much of the Midwest. Airlines set about unraveling schedules and getting travelers on their way after more than 10,000 flights were canceled over two days.
Plummeting temperatures in the central United States complicated recovery efforts, touching everything from the winter wheat crop to rail transportation to preparations for the NFL's Super Bowl on Sunday in Dallas.
More bad weather was on the way for some places. Parts of the southern United States, including Texas, Louisiana and Alabama, are forecast to get snow and ice late on Thursday.
A study released on Wednesday estimated that a state's economy can lose hundreds of millions of dollars for each day businesses are shut due to roads left impassable by storms.
The study, by Boston-based IHS Global Insight and commissioned by the American Highway Users Alliance, estimates that a one-day major snowstorm can cost a state ${esc.dollar}300 million to ${esc.dollar}700 million in direct and indirect costs.
Hourly workers are often the hardest hit, accounting for almost two-thirds of direct economic losses as businesses close for the day, according to the study. Indirect impact is felt in the restaurant, general merchandise and service station industries, it found.
The National Weather Service issued special advisories about "black ice" for New York and Boston. Wednesday's standing water on many streets and sidewalks froze overnight, making driving and walking treacherous in spots.
Chicago's Lake Shore Drive, crippled during the city's third-worst snowstorm on record, reopened on Thursday after 34 hours. Crews worked overnight to tow hundreds of cars still stranded by the storm.
City officials defended their response after hundreds of drivers and bus commuters spent Tuesday night huddled in their vehicles as the blizzard raged.
RETAIL SALES
Major U.S. retail chains from the humble to the high-end reported monthly sales on Thursday, and most did well despite the snowiest January in six years.
Retailers posted a 4.2 percent increase in sales in January at stores open at least a year, beating Wall Street forecasts for a 2.7-percent gain. [ID:nN03244603]
"Retailers weathered the storms in January, both literally and figuratively," said Michael Niemira, chief economist for the International Council of Shopping Centers.
Tangled air travel will need more time to return to normal, with hundreds of planes out of position and cold temperatures and areas of freezing rain creating new challenges.
Flightaware.com, a website that tracks air travel, showed more than 1,900 flights scrapped so far on Thursday.
The airports with the most flight cancellations were Chicago's O'Hare International, still recovering from Wednesday's blizzard, and Bush International in Houston, which is under a winter storm watch.
In New England, the weight of snow and ice caused dozens of building roofs to collapse, including a large industrial building in Easton, Massachusetts. A popular outlet mall near Boston was closed as a precaution.
Subzero temperatures in the Plains hard red winter wheat region on Thursday could harm those portions of the crop unprotected by a blanket of insulating snow, said forecasters Accuweather. Worries about the crop have already pushed up U.S. wheat prices.
This week's storm was just the latest winter blast in some areas. Boston, for example, has received almost twice its normal winter snowfall over the course of eight storms.
The cost of clean-up has blasted holes in the budgets of many cities, states and counties, which were already struggling with the aftermath of the severe recession. [ID:nN02271384]
(Additional reporting by Greg McCune, Karen Pierog and Lisa Lambert; Editing by Will Dunham)
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