While the proven Zacks Rank places an emphasis on earnings estimates and estimate revisions to find strong stocks, we also know that investors tend to develop their own individual strategies. With this in mind, we are always looking at value, growth, and momentum trends to discover great companies.Of these, value investing is easily one of the most popular ways to find great stocks in any market environment. Value investors use tried-and-true metrics and fundamental analysis to find companies that they believe are undervalued at their current share price levels.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 holds a P/E ratio of 8.88, while its industry has an average P/E of 17.22. Over the past year, CPA's Forward P/E has been as high as 33.20 and as low as -119.57, with a median of 12.78.Investors should also recognize that CPA has a P/B ratio of 2.39. Investors use the P/B ratio to look at a stock's market value versus its book value, which is defined as total assets minus total liabilities. CPA's current P/B looks attractive when compared to its industry's average P/B of 4.12. Over the past year, CPA's P/B has been as high as 3.13 and as low as 1.81, with a median of 2.54.Finally, investors should note that CPA has a P/CF ratio of 5.97. This metric takes into account a company's operating cash flow and can be used to find stocks that are undervalued based on their solid cash outlook. This stock's P/CF looks attractive against its industry's average P/CF of 18.05. Within the past 12 months, CPA's P/CF has been as high as 14.54 and as low as -30.61, with a median of 6.07.Another great Transportation - Airline stock you could consider is SkyWest (SKYW), which is a # 1 (Strong Buy) stock with a Value Score of A.SkyWest sports a P/B ratio of 0.38 as well; this compares to its industry's price-to-book ratio of 4.12. In the past 52 weeks, SKYW's P/B has been as high as 1.16, as low as 0.38, with a median of 0.64.Value investors will likely look at more than just these metrics, but the above data helps show that Copa Holdings and SkyWest are likely undervalued currently. And when considering the strength of its earnings outlook, CPA and SKYW sticks out as one of the market's strongest value stocks. Special Report: The Top 5 IPOs for Your Portfolio Today, you have a chance to get in on the ground floor of one of the best investment opportunities of the year. As the world continues to benefit from an ever-evolving internet, a handful of innovative tech companies are on the brink of reaping immense rewards - and you can put yourself in a position to cash in. One is set to disrupt the online communication industry. Brilliantly designed for creating online communities, this stock is poised to explode when made public. With the strength of our economy and record amounts of cash flooding into IPOs, you don’t want to miss this opportunity.>>See Zacks’ Hottest IPOs NowWant the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Copa Holdings, S.A. (CPA): Free Stock Analysis Report SkyWest, Inc. (SKYW): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research