The overall ratings of 4 Airlines stocks are down on Portfolio Grader this week. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Copa Holdings, S.A. Class A’s (CPA) rating weakens this week, dropping to a D versus last week’s C. Copa Holdings, S.A. Class A provides airline passenger and cargo services in Latin America. The company also gets F’s in sales growth and earnings growth. For more information, get Portfolio Grader’s complete analysis of CPA stock.

United Continental Holdings, Inc. (UAL) is having a tough week. The company’s rating falls 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.

American Airlines Group, Inc. (AAL) earns a D this week, moving down from last week’s grade of C. For more information, get Portfolio Grader’s complete analysis of AAL stock.

China Southern Airlines Company Limited Sponsored ADR Class H (ZNH) gets weaker ratings this week as last week’s C drops to a D. China Southern Airlines Company Limited Sponsored ADR Class H provides commercial airline services in the People’s Republic of China, Hong Kong, Macau, Taiwan, and internationally. The company also gets F’s in earnings surprise. For more information, get Portfolio Grader’s complete analysis of ZNH 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.