Since I work at home and the front door hinge has a slight squeak to it, I hear it each time the door is opened by the construction guys, and I hear a little swoosh sound each time the door is closed. Its not like the construction guys are leaving the door open an excessive amount of time or anything, so I couldn't figure out why we suddenly started being bothered with flies in the house.
They can be quite persistent and annoying so we feel no guilt or shame in killing them. One day I was trying to eat lunch while watching a little HGTV and 3 flies were absolutely driving me insane. I felt like Tippi Hedren in 'The Birds'.
Fly swatters are an inefficient waste of time. Flies have amazing reflexes and will surely move before you can swat them.
But Spouse found an easy way to kill flies: Windex.