Alliteration fills the poem with rough, unpredictable music and brings specific moments to life on the page. In short, it helps to dramatize the speaker's terrible situation. The punchy, plosive /b/ sounds of line 2, for example, call readers' attention to the speaker's horrific surroundings:
Through a distant shot of a building burning
This alliteration jumps out at the reader, hinting at the brutality of the attack and of the flames themselves. The poem uses this same technique in line 14:
The heat behind me is bullying, driving,
Those /b/ sounds make the heat seem menacing and forceful, as though it's out to get the speaker deliberately.
Other sounds create notably different effects. Take the sibilant alliteration in lines 7 and 8:
Does anyone see
a soul worth saving?
The speaker has established already that he is utterly, tragically alone, closer to the clouds than to the emergency services on the ground. These /s/ sounds cast a whispery hush over the speaker's call for help, creating an eerie quiet that's at odds with the chaos going on around him.
Elsewhere, the poem's sounds evoke its imagery. In line 4, for instance, the sharp /t/ alliteration of "twirling, turning" suggests the sounds of the man's shirt snapping in the wind. Broader consonance adds to the effect, filling the line with sharp, crisp sounds and growling /r/ sounds that suggest the man's effort:
that a white cotton shirt is twirling, turning.
The sounds of the poem's final two lines are similarly evocative, those dull, muffled /n/, /m/ and /f/ sounds helping to convey the speaker's sorrow and fatigue:
My arm is numb and my nerves are sagging.
Do you see me, my love. I am failing, flagging.