only higher resolution would fix that and only marginally, right?
Yes, basically. Although sharp contrast edges on the normal map would alias nevertheless to an extent. You might notice that horizontal and vertical lines are smooth, while diagonal lines become aliased...
Blurring the normalmap works too, to an extent, but that reduces the amount of detail visible and/or makes the ships look like silly putty.
Also, the amount of aliasing on the normalmap can be minimized by creating the normal map in higher resolution, and resizing the final normalmap to the intended size. But yeah, the only real way to reduce aliasing effects would be to increase normalmap size, which isn't usually feasible. The best we can do is to minimize the aliasing on the texture itself, and minimize texture compression artefacts (which cause a lot more eyesore than aliasing in my opinion).