That makes a lot more sense. The flights to Maris were in the air when the fog hit so they could be warned to not let the fog in on landing without it looking too suspicious. The flight to Erech had already landed so there was no way to tip them off about the fog in advance.
I still don’t understand. The plane was on the air, where people weren’t affected. It wasn’t going to crash, why was it a danger to the city? Or is it that they were having problems and they had to do an emergency landing in Erech?
It was a danger because if they warned them, then people would know that someone was still alive in Erech.