The proven Zacks Rank system focuses on earnings estimates and estimate revisions to find winning stocks. Nevertheless, we know that our readers all have their own perspectives, so we are always looking at the latest trends in value, growth, and momentum to find strong picks.

Of these, value investing is easily one of the most popular ways to find great stocks in any market environment. Value investors use a variety of methods, including tried-and-true valuation metrics, to find these stocks.

Zacks has developed the innovative Style Scores system to highlight stocks with specific traits. For example, value investors will be interested in stocks with great grades in the "Value" category. When paired with a high Zacks Rank, "A" grades in the Value category are among the strongest value stocks on the market today.

One company value investors might notice is Copa Holdings (CPA). CPA is currently sporting a Zacks Rank of #2 (Buy) and an A for Value. The stock is trading with a P/E ratio of 6.05, which compares to its industry's average of 17.43. Over the past year, CPA's Forward P/E has been as high as 7.06 and as low as 4.82, with a median of 6.02.

We also note that CPA holds a PEG ratio of 0.55. This metric is used similarly to the famous P/E ratio, but the PEG ratio also takes into account the stock's expected earnings growth rate. CPA's PEG compares to its industry's average PEG of 1.05. Over the last 12 months, CPA's PEG has been as high as 0.59 and as low as 0.19, with a median of 0.36.

We should also highlight that CPA has a P/B ratio of 1.69. The P/B ratio pits a stock's market value against its book value, which is defined as total assets minus total liabilities. This company's current P/B looks solid when compared to its industry's average P/B of 4.79. CPA's P/B has been as high as 2.10 and as low as 1.44, with a median of 1.78, over the past year.

If you're looking for another solid Transportation - Airline value stock, take a look at International Consolidated Airlines Group (ICAGY). ICAGY is a # 2 (Buy) stock with a Value score of A.

International Consolidated Airlines Group is currently trading with a Forward P/E ratio of 5.01 while its PEG ratio sits at 0.81. Both of the company's metrics compare favorably to its industry's average P/E of 17.43 and average PEG ratio of 1.05.

ICAGY's price-to-earnings ratio has been as high as 5.13 and as low as 3.80, with a median of 4.44, while its PEG ratio has been as high as 1.07 and as low as 0.07, with a median of 0.83, all within the past year.

Additionally, International Consolidated Airlines Group has a P/B ratio of 1.06 while its industry's price-to-book ratio sits at 4.79. For ICAGY, this valuation metric has been as high as 1.23, as low as 0.78, with a median of 1.01 over the past year.

These are only a few of the key metrics included in Copa Holdings and International Consolidated Airlines Group strong Value grade, but they help show that the stocks are likely undervalued right now. When factoring in the strength of its earnings outlook, CPA and ICAGY look like an impressive value stock at the moment.

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