What is the aircraft that the trees are behind of called?
The aircraft is airplanes.
    src        edge_attr  dst
0     0               on   16
1     0      in front of   13
2     1   to the left of    3
3     2            above   19
4     3  to the right of    1
5     5  to the right of    8
6     5  to the right of    9
7     8   to the left of    5
8     9   to the left of    5
9    12  to the right of   18
10   12  to the right of   20
11   13           behind    0
12   14  to the right of   16
13   15   to the left of   18
14   16  to the right of   19
15   16   to the left of   14
16   17               of   17
17   17          playing   17
18   18  to the right of   15
19   18   to the left of   12
20   19   to the left of   16
21   19            below    2
22   20   to the left of   12