Thanks for the responses, but I guess that my question must not have been clear enough. Yes, I know about the HIRF environment and about its potential effects on aircraft. As non-aircrew, I am interested in how it is managed in flight. The UK IAP gives guidance on a number of HIRTA (as mrmum posted), but the effects listed are related to damage to Comms/Nav equipment and possible affects on people... no mention of possible disruption to critical systems. I guess that this means that while you wouldn't hang about in them, you would not worry about flying through them. Is this the case?