Right at the same time that the jet bombers go screaming over his house, Guy Montag is finding out what his wife Millie has done. He is finding out that she has gone and swallowed her whole bottle of sleeping pills and is near death. As the bombers go past, he calls the emergency hospital.
To me, this is very symbolic. Both the society and the Montag "family" are in grave danger. There are these bombers flying over showing that the society is at danger of annihilation in war. At the same time, Millie is in danger from the pills and their family is in danger because of the fact that her life is so empty that she would (unknowingly) overdose herself in that manner.