Not sure if snapping them all together works at all in this case.
Here’s an easy way to do it: Add a flat lattice under your seats and give it some good amount of subdivisions along the bend of the plane. Then give the lattice object a shrinkwrap modifier and select the plane as the target.
Now give the seats a lattice modifier and select the lattice you’ve created. That should give you the effect you’re looking for.



Best part is this way you can easily make changes too.