Problem assembling wings as shown for LEGO Air Race Jet (Technic 42066)
The "rivet" bricks are length 2 axles (cross shaped diameter). Beneath the wings, there should be L-shaped 2x4 lift arms. These end in axle holes (also cross shaped) so the axle should fit tight in those, not fall through.
Perhaps you have positioned something erroneously, or you have skipped a step somewhere?