This week, the overall grades of 3 Airlines stocks are lower, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Slipping from a C to a D rating, Alaska Air Group, Inc. (ALK) takes a hit this week. Alaska Air Group, Inc. is an airline holding company which provides air service to passengers in multiple destinations. For more information, get Portfolio Grader’s complete analysis of ALK stock.

United Continental Holdings, Inc. (UAL) declines this week from a C to a D. United Continental Holdings, Inc. owns and operates airlines that transports persons, property and mail throughout the United States and abroad. The company also gets F’s in earnings momentum. For more information, get Portfolio Grader’s complete analysis of UAL stock.

This is a rough week for Delta Air Lines, Inc. (DAL). The company’s rating falls to D from the previous week’s C. Delta Air Lines, Inc. operates as an airline for passengers and cargo traveling throughout the United States and around the world. The company also gets F’s in earnings surprise and earnings momentum. For more information, get Portfolio Grader’s complete analysis of DAL stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.