No, I get this too. For me it seems to be related to new objects being drawn. On the ground I can repro it easily by taking up the drone, moving away from my aircraft until objects disappear due to LOD, then go back towards my aircraft; as new objects pop in, I’ll see spikes on the main thread. The more objects being drawn, the worse the spike is, also some objects seem worse than others. AI traffic is definitely the worst. As new AI is drawn, I get stutters.
For me, though, this happens mostly on the ground. When airports are being drawn in as I approach, I don’t usually see these spikes unless new AI traffic is being drawn there (AIG, in my case).
Also, how bad this is seems to relate to scenery complexity more generally. In more complex airports in more complex areas, it’s worse.
It’s maddening, and it seems to be worse since SU11 onwards, and worse again with SU12.