I remember many, many years ago buying some 3CX3000A7 tubes on the flea market at Dayton. Rather than checking the tubes in and letting the baggage handlers throw them 50ft against the concrete floor, I carried them in my hand luggage. When we went through Security I told the X Ray guys what was in my bag and of course they took the tubes out to look at them. There weren't many people going through at that time so we got into a bit of a conversation and I asked them if I could see the tubes on the X Ray. "Sure" was the answer, so I was able to check the grid structures inside the tubes on the screen - very useful! That was all before 9/11 so maybe things might be different now, but I bought some aftermarket Megasquirt engine management systems and programming units that look to the untrained eye like radio gear on a recent trip to Austin TX and there was no issue bring it in hand luggage. Taking my equipment to west Africa when I operated as C56TTY was no issue either. I think a lot depends on how you treat the security staff. A quick word of what the equipment is and a smile go a long way. Just treat people with respect. They have a job to do that benefits all of us and I for one an really glad that they do it.