While browsing SkyVector I came across these double Class B airspace limits within the same section (is that what you call it?). I'm wondering what it means and what the difference is between this and FL145/SFC.
The way SkyVector shows airspace is subtly different than shown on FAA charts. Whereas the FAA shows the combined limits in each area, SkyVector shows the limits once for each layer, even where layers overlap.
So, what you are probably seeing here is one area of FL145/35 on top of another area of 35/SFC, possibly disjoint but the labels for both areas just happened to end up near each other. Or, it may be two areas with the same boundaries but different owners or airspace classes. As a result, it’s often difficult to figure out exactly which area(s) each label applies to.
Note that while SkyVector uses official maps from the FAA in/near the US, the rest of the world is computer-generated and not nearly as useful, especially since other countries often use airspace classes in vastly different ways that can’t be represented well in SkyVector’s pseudo-FAA style. Notably, they use blue for all classes, which often confuses folks used to the FAA’s color scheme.
According to the Spanish AIP, they are indeed two stacked airspaces; TMA SEVILLA AREA 3B and TMA SEVILLA AREA 3C. For example, in 3B (the higher one):
VFR traffic is not allowed, except for State aircraft, helicopters, medical and rescue flights.
Official e-chart here: https://insignia.enaire.es/