I don't get all this hype about airships and flying things. Shoot it full of holes and it crashes to the ground all the same. None can pass the Iron Ring by air without the Hegemon's permission .-.
Anti-air defenses in WW2 were way too inefficient for that.
When the Germans began their V-1 attacks, they launched circa 100 missiles a day.
In comparison hundreds of fighters and even more ground defenses wasted tens of thousands of munitions and even then about 10% slipped through.
Worse, technically the percentage is even lower since only some 2000+ missiles ever got close to Britain out of the 8000+.
So the actual interception percentage is somewhere around 60-70%.
We talk about relatively dumb fired missiles, controlled by gyros and some good calculations beforehand.
They were also slower than Spitfires or other competitive fighters.
This is the most famous AA feat in the entire WW2.
So yeah, there are low but quite considerable chances that somebody can just fly past your borders. Be glad if they don't decide to just drop a few bombs if they are at it.