Here at Zacks, we focus on our proven ranking system, which places an emphasis on earnings estimates and estimate revisions, to find winning stocks. But we also understand that investors develop their own strategies, so we are constantly looking at the latest trends in value, growth, and momentum to find strong companies for our readers.

Of these, value investing is easily one of the most popular ways to find great stocks in any market environment. Value investors rely on traditional forms of analysis on key valuation metrics to find stocks that they believe are undervalued, leaving room for profits.

Luckily, Zacks has developed its own Style Scores system in an effort to find stocks with specific traits. Value investors will be interested in the system's "Value" category. Stocks with both "A" grades in the Value category and high Zacks Ranks are among the strongest value stocks on the market right now.

One company to watch right now is Allegiant (ALGT). ALGT is currently sporting a Zacks Rank of #1 (Strong Buy) and an A for Value. The stock holds a P/E ratio of 11.16, while its industry has an average P/E of 16.51. Over the past year, ALGT's Forward P/E has been as high as 61.81 and as low as 7.88, with a median of 10.24.

Value investors also use the P/S ratio. The P/S ratio is is calculated as price divided by sales. This is a prefered metric because revenue can't really be manipulated, so sales are often a truer performance indicator. ALGT has a P/S ratio of 0.6. This compares to its industry's average P/S of 0.62.

United Airlines (UAL) may be another strong Transportation - Airline stock to add to your shortlist. UAL is a # 1 (Strong Buy) stock with a Value grade of A.

Shares of United Airlines currently holds a Forward P/E ratio of 7.99, and its PEG ratio is 0.68. In comparison, its industry sports average P/E and PEG ratios of 16.51 and 0.83.

UAL's Forward P/E has been as high as 9.45 and as low as 3.63, with a median of 4.97. During the same time period, its PEG ratio has been as high as 1.13, as low as 0.41, with a median of 0.63.

Furthermore, United Airlines holds a P/B ratio of 2.70 and its industry's price-to-book ratio is 5.45. UAL's P/B has been as high as 2.95, as low as 1.18, with a median of 1.80 over the past 12 months.

These are just a handful of the figures considered in Allegiant and United Airlines's great Value grade. Still, they help show that the stock is likely being undervalued at the moment. Add this to the strength of its earnings outlook, and we can clearly see that ALGT and UAL is an impressive value stock right now.

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