Not complaining about your post - it is great and was the impetus to get me to write the DOT a second time.

I would prefer that people use your template and alter it a bit in any case. Sending a form letter to the DOT is about as bad as DL sending us one.

But here are some small thoughts:

Failure of delta to respondE is one spelling mistake.

"Please find attached delta's response below." sounds awkward to me. (is it "attached" or is it "below"?)

I would capitalize Delta Airlines each time it is used.

My guess is that someone just cutting and pasting your letter would include "(also copy and paste the complaint as an appedix)." That is a sure giveaway that it is a form letter.

"to address the content of the department of transportation iNquiry" is a spelling mistake.

"YVT," is nice Facebook or texting language but not something that should be used in such a letter to the DOT.