Not to worry
Airplanes are not shielded from cosmic radiation.
Our atmosphere protects us, but because airliners fly at high altitudes, airline crews do get a little more radiation each year than surface dwellers. The amount of radiation per flight is small, so travelers need not worry. A 7-hour flight is about 0.06 millisieverts, the same as 1 chest x-ray (one's annual recommended maximum is 1.0 millisievert).