This thread has become a dump for MacAir 3 beep solutions so here's my addition: I worked through the following non-invasive techniques (most listed above) a couple times each and after doing 5) it started booting. Maybe they worked as a combination or maybe it was 5 that did the trick. If none of these had worked I'd have tried the Thermal Paste solution above. However, if non-invasive works, who am I to complain! Hopefully this compilation helps someone! ---------------------------------------------------------------------------------------------- UPDATE: This happened to me a second time two months later: I have found a firm fix for my issue now: 1) power off, plug in power cord 2) Hold (left side) command + (left) option + P + R 3) while holding them, tap power and CONTINUE HOLDING the four buttons in 2 4) Computer will make a startup sound, KEEP HOLDING, computer will turn off, KEEP HOLDING, computer will startup again, you can let go only AFTER the second startup or even third startup....