I have worn HA all my life and is frequent flier, Never Ever had any experince of any problem.
As CI user, I had flown three times, first one in UK i was nervous about anything i showed the card to the Security he let me go round and be patted. Going to Austria from England, no problem but when i came home, they did take my card without looking at it and they put the card on my tray that goes through the Detector, i was protesting but with them speaking no english i took the chance to be forced through the xrays but took my ci off just in case. I emailed to my Audi about this, she said the worst case the magnet would set the detector off. CI users should be okay to go through and make sure they carry the card (in different lang depending where they go) all the times.
Last time i flew was yesterday, I have just got home from Austria, I came from different airport. I had my card in my hands, the security said put it in the tray, i said no because i would need it if it set the detector off, he had a look/read it carefully at the card, let me go round instead and was patted. it varies from airport to airport.