As Europe continues to try to get its debt ducks in a row, and a double-dip recession still threatens the U.S., cyclical industries like travel are starting to brace for impact. That could translate into serious jet lag for airline, hotel and travel booking stocks — if it keeps business travelers off the road.

Even without another full-blown recession, the travel market has begun to struggle. The Air Transport Association this week predicted a 2% drop from last year in the number of passengers traveling for the 12-day period around Thanksgiving — the busiest travel days of the year. Airlines alone have seen their income evaporate in 2011 — down 66% in the first nine months of the year compared to 2010.

Despite these latest concerns, there’s a little good news: U.S. unemployment was down a hair in October, falling to 9% from 9.1%. And many hospitality and travel stocks are doing well, proving that there’s still optimism, particularly among business travelers, according to the Global Business Travel Association.

Indeed, the business travel market is leading a recovery in the sector, growing by more than 6% in September, according to electronic booking data from Pegasus Solutions. The biggest winners have been strong conference hotels “that have pricing power the sector hasn’t seen in years.”

But a stagnant U.S. economy is prompting corporate uncertainty about business travel spending next year. “Uncertain economic conditions around the world continue to impact companies, which in turn impacts business travel plans and can lead to hesitation in spending,” said Michael McCormick, GBTA’s executive director and COO. “However, business travel spending growth remains vibrant, and the current environment does not portend a dramatic travel slowdown.”

Here are six bellwether travel stocks to watch in case Europe’s woes and other economic headwinds threaten to ground business travelers:

Orbitz Worldwide

What European-travel slowdown? Better than expected third-quarter earnings and a 31% jump in international bookings drove Orbitz (NYSE:OWW) stock up nearly 55% last week. Still, the online travel agency’s domestic bookings slipped 4% — largely on a jump in airline ticket prices. At $2.98, OWW is starting to bounce back from its 52-week low of $1.57 on Oct. 4. With a market cap of $308 million, the stock has a price/earnings-to-growth ratio of 1.46, indicating that it is overvalued.

Expedia

Expedia (NASDAQ:EXPE), which missed third-quarter revenue expectations last week, also reported weaker growth in domestic bookings (a theme that likely will be repeated after the bell Monday when Priceline (NASDAQ:PLCN) releases its quarterly earnings). EXPE’s international bookings rose 21%, while domestic bookings grew only 4%. Company executives voiced concerns about weakness in southern Europe and a cautionary note about the economy. At $28.37, EXPE has battled back from its 52-week low of $19.61 in March. With a market cap of about $7.8 billion, EXPE has a PEG ratio of 1, which means it’s fairly valued. It pays a 1% current dividend yield.

Delta Air Lines

With fuel price volatility and fewer passengers, it’s a bad time for the airline sector in general. But any airline that can score big with business travelers is worth a second look. For the first time ever, Delta (NYSE:DAL) ranked first in Business Travel News’ annual airline survey, earning the highest ratings from corporate travel buyers in five out of 10 service delivery categories. At $8.35, DAL is 30% higher than its 52-week low of $6.41 in August. With a market cap of nearly $7.1 billion, Delta has a PEG ratio of about 1.2, meaning it’s fairly valued.

US Airways

US Airways (NYSE:LCC) finished third in BTN’s survey behind United Continental (NYSE:UAL) — a big improvement from last year, when it ranked dead last. “Corporate travel buyers have recognized a more active and flexible US Airways,” the survey said. LCC earned top honors on overall price value and relationships with account managers. At $5.50, US Airways is trading 21% above its 52-week low of $4.53 last month. With a market cap of $892 million, LCC has a PEG ratio of 1.19.

Starwood Hotels & Resorts

High-end travelers helped Starwood Hotels & Resorts‘ (NYSE:HOT) third-quarter earnings beat the Street last week — Starwood reversed last year’s $6 million loss into a $163 million profit. The company’s St. Regis, W, Luxury Collection and Westin resorts — as well as the Away Spa — made big contributions to the bottom line. Still, Starwood executives say they are seeing some softening demand in Europe and Japan. At $50.63, HOT shares have recovered 38% since their 52-week low of $35.76 last month. With a market cap of $9.9 billion, the stock has a PEG ratio of 0.92, meaning that the stock is undervalued. HOT has a current dividend yield of 0.59%.

Hyatt

One-time charges drove Hyatt’s (NYSE:H) quarterly income down more than 50%, company officials said last week. Although H missed analysts’ third-quarter estimates, revenue rose 2% to $897 million, and revenue per available room (revpar) rose by 9.2%. Its higher-end brands and international properties drove Hyatt’s revpar growth, a key hotel industry measurement. At $37.01, H is trading 24% above its 52-week low of $29.18 last month. With a market cap of $6.1 billion, Hyatt has a PEG ratio of 4.94, indicating the stock is overvalued.

Bottom Line

While these travel stocks are profiting from growth in the high-end, business travel and international businesses right now, failure to resolve the euro zone crisis could have a serious impact on their fortunes.

As of this writing, Susan J. Aluise did not hold a position in any of the aforementioned stocks.