Sorry to hear about your grandfather's passing.

Best place is to fill out the web form at www.united.com/feedback. It will have a place to fill out your basic info, PNR info., etc. (and will allow you to login to pre-fill out the info. from your profile like name, MP #, etc.).

Make sure you keep any complaint short and to the point - anything other than the facts are unimportant and will only take away from the legitimate complaints. Also, keep out snark and comments like "I swear they take away legroom by the day" which a, is not true, and b, will, again, only take away from any legitimate concerns.

I find using bullets if there are more than a couple of issues is a good way to keep everything organized, concise, and also easily differentiates between point a, b and c, etc. So you can start with a brief opening paragraph with info, say, here are the issues I encountered, go to bullets, and then close, potentially putting in what you expect from them.

It also may be a good idea to write it up in a program like Word, then copy and paste to a text editor (notepad, etc.) to strip out any code, then paste into the web form and submit.

Good luck.