Today, Bernstein upgraded American Airlines Group (AAL), but the firm reinforced the negative view of the airline with only a Market Perform rating. The stock has jumped to $45 despite the Bernstein price target only moving to $43. The recent $5 dip still provides a buying opportunity. The airline stock only trades at 8x forward EPS estimates and trades at a huge gap to the smaller Delta Air Lines (DAL). American Airlines is still working with lower margins due to revenue management and integration issues with US Airways still in the works. Analysts estimate that American has the ability to produce $3 billion in additional revenues to match the performance of Delta Air Lines. More research on this subject: American Airlines: The Wrong ReactionBerstein favors Delta Air Lines, but the recommendation is that American Airlines eventually closes the valuation gap that is currently some 50% higher. Disclosure: Long AAL