Since I've been off work and on lockdown for over two months now, questions like how to pronounce Aetna may as well be a matter of life and death.
Sensitive forumites (not "formites", a word of whose meaning I was blissfully unaware until the virus reared its crownèd head) having received adequate warning, I think it's reasonably safe to reveal my onetime co-worker's interesting and, hopefully, non-fatal pronunciation of the word. I've taken the precaution of coloring it white on white. Any hardy souls willing to risk exposure should use their mouse to select the invisible text that follows this, preferably while sitting and wearing appropriate eye protection.
AY-eht-nuh
Neither I nor Tim Berners-Lee accept any liability for incidental or consequential damages resulting from the viewing of this pronunciation. Once it has been seen, it may remain with you for the rest of your life and, indeed, that of your descendants to the seventh generation. You have been warned: it cannot be unseen.