Muscovy duck question hatching egg under duck

[kat79]

Hi first time allow a duck to hatch some eggs, her eggs are at day 35 but ducks still havent broken into the airsac but are really pushing against it as you can see a shadow in the airsac when candling. How long would others leave them before intervening? They are still alive at the moment.

 

[ChickenCanoe]

I wouldn't intervene at all.
Ducks have been incubating their eggs for millions of years without human intervention.
If it were me, I wouldn't bother her at all to candle or anything else. The more hands off I am, the more successful the hens are. Hatch day is definitely the time to leave them alone.
Messing around with a broody nest on hatch day is akin to opening an incubator when pipping is going on.