The ratings of four Distributors stocks are down this week, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Kaman Corp.‘s (NYSE:KAMN) rating falls to a D (“sell”) this week, down from C (“hold”) the week prior. Kaman serves government and commercial markets through its diversified technologies and distribution segments. For more information, get Portfolio Grader’s complete analysis of KAMN stock.

Aircastle (NYSE:AYR) gets weaker ratings this week as last week’s C drops to a D. Aircastle is engaged in acquiring, leasing, and selling commercial jet aircrafts to passenger and cargo airlines throughout the world. The stock also rates an F in Cash Flow. To get an in-depth look at AYR, get Portfolio Grader’s complete analysis of AYR stock.

AerCap‘s (NYSE:AER) rating weakens this week, dropping to a D versus last week’s C. AerCap operates as an integrated aviation company worldwide. The stock gets F’s in Cash Flow and Sales Growth. For a full analysis of AER stock, visit Portfolio Grader.

Willis Lease Finance (NASDAQ:WLFC) earns a D this week, falling from last week’s grade of C. Willis Lease Finance leases commercial aircraft engines and other aircraft-related equipment to air carriers, manufacturers, and overhaul/repair facilities worldwide. The stock gets F’s in Cash Flow and Sales Growth. The stock price has fallen 11.4% over the past month, worse than the 4% increase the Nasdaq has seen over the same period of time. To get an in-depth look at WLFC, get Portfolio Grader’s complete analysis of WLFC 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.