Air crews are exposed to various types of radiation from space, also known as cosmic radiation. Such high-energy and high-charge particles create damage along a linear track in the cell, produce secondary elements and create reactive oxygen species that further damage cellular macromolecules and structures. Double-stranded break repair by means of homologous recombination is inhibited as Bcl2 is overexpressed due to high-energy particles damaging the Bcl2 gene. Damage to the p53 gene causes decreased expression of p21 thereby disrupting the time frame that is normally available for DNA repair. A lack of p53 prevents antioxidant formation allowing for reactive oxygen species to inflict additional damage. Telomere dysfunction in chromosomes creates further genomic instability. Genomic instability contributes to the formation of cancerous cells. Regular exposure to charged particles from space, which are more prevalent at higher altitudes, imposes a health risk to air crew and people who travel by air frequently.