"Days of the week with the most midair collisions were Saturday (21.8%) and Sunday (22.4%), with 10.9– 13.5% each day Tuesday through Friday, and 5.8% on Monday."
From "Midair Collisions: Limitations of the See-and-Avoid Concept in Civil Aviation" by C. Craig Morris.
Fly on a Monday - hardly anyone flies on Mondays. At least they didn't till I posted this.