The short answer is yes. I have seen fogging from airport hand luggage x-ray machines after just 3 or 4 passes (this was using UK and USA not 3rd world airports!).
I always use FP4 medium speed film (125 ISO) so it happens on this, not just high speed films as airport staff would have you believe. I used to work for Ilford Photo and ran the world-wide customer service area for product problems and saw lots of examples of airport x-ray fogging from around the world. The fogging I have seen on my film I know not to be an isolated incidence.
There are 3 ways around this that I use:
1. Have film delivered to my address at the destination I am travelling to (hotel or friends, etc.) by a supplier in that country.
2. Ask for hand search of film at airport hand luggage x-ray areas. You have a legal right to a hand search on film in the USA unless they are on red alert for terrorism. I have never been refused a hand search in the USA and I have had dozens of them at Newark, JFK, Boston, Chicago, Denver and San Francisco. I have also had hand searches of my film at Amsterdam, Berlin, Rome, Vienna, Hong Kong, Sydney, Auckland and Christchurch airports. I try and avoid flights in Europe, preferring to drive. This is specifically to avoid airport x-ray scans. I always carry my film in clear plastic bags (I use Ortlieb A3 map cases as they are large, very stong, have a velcro closure to secure the films inside and are crystal clear with a carry chord).
3. Have film processed locally when on a trip. This can be done but is difficult as there are not many good b&w labs left.
I have seldom managed to have a hand search at UK airports even though I know that they have the same equipment as is used at USA airports and most others around the world. Consequently, I always travel to the airport for the flight leaving the UK by car or train, I don’t use UK connecting flights.
There is an excellent lab in New York – Chelsea Photographic. They often turn jobs around the same day. If I’m in NYC I use them. Make sure you let them know to expect you and roughly how many films they will have to process.
I have also used Reed Photo in Denver and Image Lab in Wellngton, New Zealand
Mostly I bring exposed films back here for processing and endure the hand searches. In the UK for processing large batches of film I use Ilford Lab Direct. Up to 30 rolls, I process myself.