I'm seeing a lot of folks dropping articles. It's also becoming quite common to eliminate pronouns at the beginning of sentences, i.e., instead of "I went down to the store" you write "Went to the store"
I use this purposefully to jar the reader. I have no idea what the underlying linguistic reasons are.
You're probably demonstrating this on purpose: your very first sentence is itself an example of dropping a pronoun + verb.
It's considered standard to write in formal, passive, third-person tone. [2]
During undergrad, I was constantly drilled to make my writings as concise as possible.
[1] http://www2.aje.com/en/education/other-resources/articles/ed... [2] http://writingcenter.unc.edu/handouts/passive-voice/
They almost feel like "uncountable" nouns, but I'm not sure. "Flight" can be countable, but as a generalized state/phase, I think it wouldn't be. It doesn't sound strange to me (a native speaker).
It would not be wrong to use "the" for many/all of these cases, but it would have changed the meaning, somewhat.
[1] http://www.edufind.com/english-grammar/definite-article/