"he followed the bombs all the way down through the Plexiglas nose"
Bombardier's nose compartment on a Boeing B-17G, made of Plexiglas, 1944
Plexiglas is a trademark name for a light, transparent, weather-resistant thermoplastic, Poly (methyl methacrylate), commonly used for combs, plastic sheeting, and other applications. It offers a shatter-resistant alternative to glass, and is often spelled lower-case with a second “s,” as plexiglass.
Developed in 1928, it was first marketed under this name in 1933 by Rohm and Haas Company. To say lead bombardier Havermeyer “followed the bombs all the way down through the Plexiglas nose” means he watched with interest as they fell and hit their targets without ordering any evasive action by his plane, flying straight and true and terrifying the rest of the crew because they felt like sitting ducks for German antiaircraft fire.