Delta Air Lines' stock has gained 66% over the past three years but has struggled with a recent 2.1% decline over the last year, contrasting with a robust 55% annual growth in earnings per share. Despite this, long-term shareholders have seen a steady gain of 10% per year over five years. The airline's low P/E ratio of 8.54 indicates potential undervaluation, while total shareholder return of 71% over three years outpaces the share price performance, prompting investors to evaluate future projections.