extruding between cross-sections.......

[eldonb]

Well, maybe, here are some ideas,

In vertex mode, select the two cross sections and then click on
Vertex -> Vertex Create Convex Surface/Object

Then, if necessary delete the end surfaces: in vertex mode select all of the vertex that make up one end, shift to surface mode, press delete.

Or, because most air-frames do not have concaved surfaces, select as many cross sections as you can and then do the "Vertex Create Convex Surface/Object" operation on all of them. If there is a concaved surface that need to be created ( for example lower edge of a head rest section) move the concaved vertexes out create the Surface and the move the vertex back to the correct location.

Hope this helps,
Eldon