Why was “aerospace” removed from “Popular Keywords” and how can we get it put back on there?
Popular keywords are based on recent usage. On a day when Sukhoi-30mki posts a lot of articles, the keyword 'aerospace' gets used often enough to appear on the list.
What I have done is to add the keywords 'aerospace' and 'navair' (and 'banglist') to my custom sidebars, so that the latest keyword tagged articles appear on my sidebar automatically.
Click on the "configure sidebar" at the end of your own sidebar to get rid of unwanted boxes such as breaking news, and add custom boxes for your favorite keywords.