Lyric discussion by baclightning 

Cover art for Boeing 737 lyrics by Low Anthem, The

But why Boeing 737? Neither of the aircraft that hit the Twin Towers was a Boeing 737. Both were Boeing 767s. Since the word "767" fits into the song's meter exactly the same as "737", why was "737" chosen?

Though having the same number of syllables, "thirty" is far more mellifluousness in this context than "sixty":

The sounds involved in singing "six-ty" would be far more clumsy here than "thir-ty". First in 767 you have the repeating "S" sounds of "SSSeven SSSixty SSSeven" with a clumsy thudding tripping "ixDee" right in the middle and they you have to try and get right back up to another "S"

The "thirty" sound can be vocally tapdanced over without requiring any awkward stressing of the sounds, and...