1. He thought that by the year 2000, people could fly in personal airplanes and flying police officers would control airplanes in the air.
2. He thought that by the year 2000, people could fly "on" personal airplanes and flying police officers would control airplanes in the air.
(Can we use 'on' instead of 'in'? Which one is common?)
3. He thought that by the year 2000, people could fly in personal airplanes and flying police officers would control airplanes "in the air."
(What is the part of speech of "in the air"? Is it an adjective phrase or an adverbial phrase?)
4. He thought that by the year 2000, people could fly in personal airplanes and flying police officers would control "the" airplanes "in the air."
(Is this sentence the same as #3? If we put 'the' before 'airplanes', does 'in the air' modify 'the airplane'?)
1 and 2 -- Think about this: Do people (pilots or passengers) go inside an airplane or sit on top of it? Use "in," please!!
3. "in the air" is a prepositional phrase being used to tell WHERE, so the prepositional phrase is being used as an adverb, modifying the verb "control." [A case could be made that this prep phrase is being used as an adjective, modifying "airplanes," but I lean toward the adverbial use.]
4. There is no real difference in meaning between 3 and 4, whether "the" is in there or not. That prepositional phrase still modifies "control."
In all these sentences, you need a comma after "that" and a comma after the first instance of "airplanes."
He thought that, by the year 2000, people could fly in personal airplanes, and flying police officers would control airplanes in the air.
http://mentalfloss.com/article/51362/4-changes-english-so-subtle-we-hardly-notice-theyre-happening?utm_source=Facebook&utm_medium=Partner&utm_campaign=FBK
This is an interesting article about the slow, long-term changes that have been taking place in English. You can be sure changes in grammar and vocabulary are happening in all languages over time. What's really interesting to me is how long some of these have been in their changing phase!
1. To understand this sentence, we need to look at the verb "fly" and how it is being used. The phrase "fly in personal airplanes" indicates that people would be able to travel by air using their own airplanes. The second part of the sentence suggests that there would be flying police officers controlling the airplanes while they are in the air. This sentence is expressing the speaker's belief or thought about a futuristic scenario.
2. In this sentence, using "on" instead of "in" changes the preposition used to describe how people would fly. "Fly on personal airplanes" suggests that people would be flying while standing or being positioned on top of their personal airplanes. The phrase "in personal airplanes" is more commonly used as it implies that people would be inside the airplanes while flying.
3. "In the air" is an adverbial phrase in this sentence. It functions to specify where the action of flying and the control of airplanes by police officers takes place. Adverbial phrases modify verbs, and in this case, "in the air" is telling us where these actions are happening.
4. The sentence you provided, "He thought that by the year 2000, people could fly in personal airplanes and flying police officers would control the airplanes in the air" is the same as sentence 3. Using "the" before "airplanes" helps to specify that the speaker is referring to specific airplanes rather than any generic ones. The phrase "in the air" still modifies the overall action of "control," indicating that the control would take place while the airplanes are in the air.