NEW YORK (TheStreet) --  United Airlines (UAL - Get Report) grounding flights earlier this week due to computer malfunctions is not slowing down many travelers. Nor are travelers deterred by the recent Department of Justice announcement that it is launching an investigation into possible collusion in the airline industry. And the hotel industry is set to do well, despite Airbnb and other industry disruptors.

Spending on travel and tourism increased in the first quarter of 2015 reported the Bureau of Economic Analysis, despite the anemic growth in the economy in the same period. Historically, the hospitality industry, despite its pronounced cyclical behavior, manages to grow on par with the economy long term.

So, what are the best hotels, resorts, and cruise lines investors should be buying? Here are the top four, according to TheStreet Ratings,TheStreet's proprietary ratings tool.

TheStreet Ratings projects a stock's total return potential over a 12-month period including both price appreciation and dividends. Based on 32 major data points, TheStreet Ratings uses a quantitative approach to rating over 4,300 stocks to predict return potential for the next year. The model is both objective, using elements such as volatility of past operating revenues, financial strength, and company cash flows, and subjective, including expected equities market returns, future interest rates, implied industry outlook and forecasted company earnings.

Buying an S&P 500 stock that TheStreet Ratings rated a buy yielded a 16.56% return in 2014 beating the S&P 500 Total Return Index by 304 basis points. Buying a Russell 2000 stock that TheStreet Ratings rated a buy yielded a 9.5% return in 2014, beating the Russell 2000 index, including dividends reinvested, by 460 basis points last year.

Check out which hotels, resorts, and cruise lines made the list. And when you're done, be sure to read about which semiconductor stocks to buy now. Year-to-date returns are based on July 10, 2015, closing prices. The highest-rated stock appears last.

IILG ChartIILG data by YCharts
4. Interval Leisure Group, Inc. (IILG)

Rating: Buy, B+
Market Cap: $1.3 billion
Year-to-date return: 6.9%

Interval Leisure Group, Inc., together with its subsidiaries, provides lodging and leisure services to the vacation industry in the United States, Europe, and internationally. The company operates through two segments, Exchange and Rental, and Vacation Ownership.

"We rate INTERVAL LEISURE GROUP (IILG) a BUY. This is driven by multiple strengths, which we believe should have a greater impact than any weaknesses, and should give investors a better performance opportunity than most stocks we cover. The company's strengths can be seen in multiple areas, such as its robust revenue growth, reasonable valuation levels, increase in net income, good cash flow from operations and increase in stock price during the past year. We feel its strengths outweigh the fact that the company has had generally high debt management risk by most measures that we evaluated."

Highlights from the analysis by TheStreet Ratings Team goes as follows:

  • The revenue growth came in higher than the industry average of 7.3%. Since the same quarter one year prior, revenues rose by 17.5%. This growth in revenue appears to have trickled down to the company's bottom line, improving the earnings per share.
  • The net income growth from the same quarter one year ago has significantly exceeded that of the S&P 500 and the Hotels, Restaurants & Leisure industry. The net income increased by 6.5% when compared to the same quarter one year prior, going from $23.72 million to $25.26 million.
  • Net operating cash flow has significantly increased by 89.99% to $64.71 million when compared to the same quarter last year. In addition, INTERVAL LEISURE GROUP has also vastly surpassed the industry average cash flow growth rate of -11.01%.
  • After a year of stock price fluctuations, the net result is that IILG's price has not changed very much. Although its weak earnings growth may have played a role in this flat result, don't lose sight of the fact that the performance of the overall market, as measured by the S&P 500 Index, was essentially similar. Turning our attention to the future direction of the stock, it goes without saying that even the best stocks can fall in an overall down market. However, in any other environment, this stock still has good upside potential despite the fact that it has already risen in the past year.
RCL ChartRCL data by YCharts
3. Royal Caribbean Cruises, Ltd. (RCL - Get Report)

Rating: Buy, B+
Market Cap: $18.1 billion
Year-to-date return: -0.02%

Royal Caribbean Cruises, Ltd. operates as a cruise company. The company operates cruisers under the Royal Caribbean International, Celebrity Cruises, Pullmantur, Azamara Club Cruises, CDF Croisieres de France, and TUI Cruises brand names.

"We rate ROYAL CARIBBEAN CRUISES LTD (RCL) a BUY. This is driven by a number of strengths, which we believe should have a greater impact than any weaknesses, and should give investors a better performance opportunity than most stocks we cover. The company's strengths can be seen in multiple areas, such as its solid stock price performance, impressive record of earnings per share growth, compelling growth in net income, reasonable valuation levels and good cash flow from operations. We feel its strengths outweigh the fact that the company has had generally high debt management risk by most measures that we evaluated."

Highlights from the analysis by TheStreet Ratings Team goes as follows:

  • Powered by its strong earnings growth of 66.66% and other important driving factors, this stock has surged by 41.34% over the past year, outperforming the rise in the S&P 500 Index during the same period. Regarding the stock's future course, although almost any stock can fall in a broad market decline, RCL should continue to move higher despite the fact that it has already enjoyed a very nice gain in the past year.
  • ROYAL CARIBBEAN CRUISES LTD reported significant earnings per share improvement in the most recent quarter compared to the same quarter a year ago. The company has demonstrated a pattern of positive earnings per share growth over the past year. We feel that this trend should continue. During the past fiscal year, ROYAL CARIBBEAN CRUISES LTD increased its bottom line by earning $3.42 versus $2.14 in the prior year. This year, the market expects an improvement in earnings ($4.56 versus $3.42).
  • The net income growth from the same quarter one year ago has significantly exceeded that of the S&P 500 and the Hotels, Restaurants & Leisure industry. The net income increased by 71.0% when compared to the same quarter one year prior, rising from $26.46 million to $45.23 million.
  • Net operating cash flow has increased to $426.43 million or 35.03% when compared to the same quarter last year. The firm also exceeded the industry average cash flow growth rate of -11.01%.
CCL ChartCCL data by YCharts
2. Carnival Corporation (CCL - Get Report)

Rating: Buy, A
Market Cap: $39.4 billion
Year-to-date return: 11.6%

Carnival Corporation operates as a cruise company worldwide. It provides vacations to various cruise destinations.

"We rate CARNIVAL CORP/PLC (USA) (CCL) a BUY. This is based on the convergence of positive investment measures, which should help this stock outperform the majority of stocks that we rate. The company's strengths can be seen in multiple areas, such as its solid stock price performance, impressive record of earnings per share growth, compelling growth in net income, reasonable valuation levels and good cash flow from operations. We feel its strengths outweigh the fact that the company shows low profit margins."

Highlights from the analysis by TheStreet Ratings Team goes as follows:

  • Powered by its strong earnings growth of 123.07% and other important driving factors, this stock has surged by 32.27% over the past year, outperforming the rise in the S&P 500 Index during the same period. Regarding the stock's future course, although almost any stock can fall in a broad market decline, CCL should continue to move higher despite the fact that it has already enjoyed a very nice gain in the past year.
  • CARNIVAL CORP/PLC (USA) reported significant earnings per share improvement in the most recent quarter compared to the same quarter a year ago. The company has demonstrated a pattern of positive earnings per share growth over the past year. We feel that this trend should continue. During the past fiscal year, CARNIVAL CORP/PLC (USA) increased its bottom line by earning $1.57 versus $1.38 in the prior year. This year, the market expects an improvement in earnings ($2.50 versus $1.57).
  • The net income growth from the same quarter one year ago has significantly exceeded that of the S&P 500 and the Hotels, Restaurants & Leisure industry. The net income increased by 126.5% when compared to the same quarter one year prior, rising from $98.00 million to $222.00 million.
  • Net operating cash flow has increased to $1,515.00 million or 26.67% when compared to the same quarter last year. The firm also exceeded the industry average cash flow growth rate of -11.01%.

VAC ChartVAC data by YCharts
1. Marriott Vacations Worldwide Corporation (VAC - Get Report)

Rating: Buy, A+
Market Cap: $3 billion
Year-to-date return: 23%

Marriott Vacations Worldwide Corporation develops, markets, sells, and manages vacation ownership and related products under the Marriott Vacation Club and Grand Residences by Marriott brands.

"We rate MARRIOTT VACATIONS WORLDWIDE (VAC) a BUY. This is based on the convergence of positive investment measures, which should help this stock outperform the majority of stocks that we rate. The company's strengths can be seen in multiple areas, such as its revenue growth, largely solid financial position with reasonable debt levels by most measures, solid stock price performance, impressive record of earnings per share growth and compelling growth in net income. We feel its strengths outweigh the fact that the company shows weak operating cash flow."

Highlights from the analysis by TheStreet Ratings Team goes as follows:

  • The revenue growth came in higher than the industry average of 7.3%. Since the same quarter one year prior, revenues rose by 13.2%. Growth in the company's revenue appears to have helped boost the earnings per share.
  • The current debt-to-equity ratio, 0.57, is low and is below the industry average, implying that there has been successful management of debt levels.
  • Powered by its strong earnings growth of 90.74% and other important driving factors, this stock has surged by 57.07% over the past year, outperforming the rise in the S&P 500 Index during the same period. Regarding the stock's future course, although almost any stock can fall in a broad market decline, VAC should continue to move higher despite the fact that it has already enjoyed a very nice gain in the past year.
  • MARRIOTT VACATIONS WORLDWIDE reported significant earnings per share improvement in the most recent quarter compared to the same quarter a year ago. The company has demonstrated a pattern of positive earnings per share growth over the past two years. We feel that this trend should continue. During the past fiscal year, MARRIOTT VACATIONS WORLDWIDE increased its bottom line by earning $2.30 versus $2.17 in the prior year. This year, the market expects an improvement in earnings ($3.48 versus $2.30).
  • The net income growth from the same quarter one year ago has significantly exceeded that of the S&P 500 and the Hotels, Restaurants & Leisure industry. The net income increased by 79.2% when compared to the same quarter one year prior, rising from $19.00 million to $34.05 million.