David Clark Pro-X (very good)
Flying with a pair of those on a KingAir, very happy!
Not as quiet as the A20 but MUCH lighter and WAY less clamping on your head. With the DC Pro X you will need to find the sweet spot on your ears where the cups have to sit in order to make the most of the (limited) passive NR, then the active NC will do the rest. You can still hear engines buzzing, gear and flaps motors but nothing worse than driving in your car on the highway.
Mind the DC comes with the same "intelligent" battery life management as the A20 but Bluetooth is standard issue for 2/3 of the price...everybody wins!