Both are pretty small
Radiation dsoes are measured in Sieverts
Flying at 35,000 feet typically exposes you to about 6 microSieverts (that's 6 millionths of a Sievert) per hour
http://www.solarstorms.org/FAAAirlines.html
A chest X-ray exposes you to about 100 microSieverts so about 16 hours flying by my maths.
But the figures will vary depending on the type of X ray and how active the solar radiation is during the "flight".
What is a "safe" level of exposure depends - you could be walking about the street today and get hit by a single decay event from the granite in the pavement and it could give you cancer - but the odds against it are so extreme
The limit for public exposure is 1 millisieverts which is 1,000 Microsieverts
10 x-rays or 160 hours flying
That is still a very low level - the level set down to protect workers is still 20 times higher
200 x-rays worth