Double Whammy
No-one's mentioned the obvious yet, but noise cancelling earbuds under noise cancelling heaphones is possibly the best way to truly cancel noise and still consume content. Earbuds with NC+ connected to device via BT and the headphones on NC duty only.
Works really well as long as the headphones are roomy enough. Plus they can help secure the earbuds in place so no fear on losing one on a long-haul flight. If the earbuds run out of juice then the overears will still keep cabin noises in check.
If silence is important tho, I'd 100% recommend custom earplugs (e.g. Ultimate Ear sleep plugs).
-31db with no batteries, no NC hiss and they're seriously comfortable
Silence through insulation.