In "Fahrenheit 451" what are the parallel states in Montag's life and the conditions in the city (war) as the story progresses?
from the contentment of Montag's initial life as a devoted fireman to the turmoil in his life when he finds the unvarnished truth about books and the need learn about them
The increasing conflict and ominous foreshadowings of war tend to pick up the pace as Montag becomes more and more conflicted; in a way, the jet bombers increase in frequency as Montag becomes more turmoiled, so, they represent his own war within himself. The very first hint at the jet bombers is right after he discovers Mildred, nearly dead, after her suicide attempt. Right after his discovery of her cold body, the book hints at the war:
"As he stood there the sky over the house screamed....Montag was cut in half. He felt his chest chopped down and split apart. The jet bombers going over, going over, going over..."
Bradbury uses these jets to represent Montag's horror at what Mildred has done, and his conflicting emotions that were stirred up from his meeting with Clarisse. Notice how he was "cut in half" by the bombers; this symbolizes how part of Montag is in his old, blissfully ignorant world, part of it is in the world of change.
As the story continues, the bombers are mentioned more and more frequently, as Montag increases his hunt for happiness, and steps closer to all-out war against society. As he is trying to read with Mildred, and in anguish over what books mean, "the bombers crossed the sky and crossed the sky" over them, and as soon as Montag and Faber decide to plant books and start to undermine the system, Bradbury notes that "a bomber flight had been moving east all the time" that they had been talking. So, almost every time that Montag is conflicted, the bombers enter the scene. This culminates in the end scene where he has finally declared war on society, and watches as true war is launched on his city, and it is torched.
I hope that those thoughts help a bit; it's an interesting question! Good luck!