taking a flight

In flight there are two principal sources of natural radiation to consider:

1. Galactic Cosmic Rays (GCR) which are always present, and
2. Solar Energetic Particle (SEP) events, sometimes called Solar Cosmic Ray (SCR) events, which occur sporadically.

Galactic cosmic rays are chiefly high-speed protons and helium ions.
Most gamma rays from the outer space are absorbed by earth's atmosphere at a typical flight altitude.
UV is shielded by the aircraft effectively if one stays inside the aircraft.

The page includes an image showing the absorption of em radiation by the atmoshpere:
http://amazing-space.stsci.edu/resources/explorations/groundup/lesson/basics/g17b/index.php

Further reading:
http://en.wikipedia.org/wiki/Cosmic_ray
http://en.wikipedia.org/wiki/Galactic_cosmic_ray
http://www.sec.noaa.gov/info/RadHaz.html