So in a previous version, sometimes a Hybrid Keep would manifest as a Landing Site and that would be like an active large-scale operation that would wreck that countries opinion of xcom and slaughter ratings for unwary players.
In this version, the Hybrid Keep is a base(or mansion-like or what have you), but I'm not 100% sure if it has the same dynamic, does it? I've only encountered one so far.
In that game Xenonauts, there is a new type of air-only alien encounter attack, and it seems like this game does include air-only UFO flybys, but they don't seem to have the same effect as the Alien Terror missions, that I can tell.
Would it be feasible to have a large ship landing site with a detection radius, that would sit and wreck ratings, but 1) spawn interceptors when Xcom craft approached, and also/or 2)took off to aerially fight XCom? The drawbacks might be if players couldn't know it was an alien aerial bombardment or not, so they'd have to send xcom fighters along with transport, but personally I do that anyway b/c battleships are already pretty dangerous with one.
Edit: Or, for this "Air Terror" variant, it would keep landing but only for a split second, about +50 times in a row