Right now, American Airlines Group Inc. AAL share price is at $15.15, after a 5.31% drop. Over the past month, the stock increased by 35.91%, but over the past year, it actually decreased by 51.57%. With questionable short-term performance like this, and great long-term performance, long-term shareholders might want to start looking into the company's price-to-earnings ratio.

The stock is currently above from its 52 week low by 83.64%. Assuming that all other factors are held constant, this could present itself as an opportunity for investors trying to diversify their portfolio with Airlines stocks, and capitalize on the lower share price observed over the year.

The P/E ratio is used by long-term shareholders to assess the company’s market performance against aggregate market data, historical earnings, and the industry at large. A lower P/E indicates that shareholders do not expect the stock to perform better in the future, and that the company is probably undervalued. It shows that shareholders are less than willing to pay a high share price, because they do not expect the company to exhibit growth, in terms of future earnings.

Most often, an industry will prevail in a particular phase of a business cycle, than other industries.

Compared to the aggregate P/E ratio of the 10.33 in the Airlines industry, American Airlines Group Inc. has a lower P/E ratio of 0.0. Shareholders might be inclined to think that they might perform worse than its industry peers. It’s also possible that the stock is undervalued.

price to earnings ratio is not always a great indicator of the company's performance. Depending on the earnings makeup of a company, investors may not be able to attain key insights from trailing earnings.