Are there pilots or airplanes?
No, there are no airplanes or pilots.
   src        edge_attr  dst
0    1  to the right of    6
1    1   to the left of    8
2    1  to the right of   15
3    6   to the left of    1
4    6   to the left of   15
5    8  to the right of    1
6    9   to the left of   12
7   12  to the right of    9
8   15  to the right of    6
9   15   to the left of    1