Just got back from a pretty intense international vacation. While traveling, I had my own pump (which I was wearing), a back-up pump, and all my supplies. I always carried with me a note from my doctor describing the things that I have to keep on me at all times (insulin, pump supplies, syringes, juice). However, in the course of traveling 4 flights and getting through 6 separate security lines (both here in the U.S. and abroad), I was never once asked for the note or question why I had any of the items in my bag.
When I got to the front of the line, I informed the security guard that I was wearing a pump and also had a spare insulin pump that needed to be hand checked. I go through metal detectors wearing my own pump. However, I DO NOT subject either pump (my own or the one borrowed from Minimed) to X-rays. This means I DO NOT send the spare pump through the x-ray machine and I do not go through the backscatter x-ray scanners wearing my own pump. If the airport uses a backscatter body scanning machine, I simply ask for a pat down.
I had few issues. The only issue I had that annoyed me was a TSA agent here in the US insisting that I could wear my pump in the backscatter x-ray scanner. I showed her the Minimed insert which clearly states that the pumps should not be exposed to x-rays and she just said, "Well, I have seen other people go through." I explained to her that the x-rays could cause the pump to malfunction and could result in someone dying quickly if a whole lot of insulin was dumped into them at once. I explained to her that our pumps generally contain 3-4 days' worth of insulin, and that if all that insulin went into a person at once they could die. I was nice/curteous, but emphasized the "death" part.