extending all the way across / running all the way through
亘
=
二
+
日
:
Mnemonic symbol: in this character the sun goes from horizon to horizon, and thus I choose to represent it by a contrail.
Guy Fawkes wants to find out where contrails really come from, so he follows one until he arrives at the encampment's bathroom. There he finds that the sun was experimenting with a capacitor. She blew the capacitor up accidentally, resulting in lots of smoke, which then formed this contrail.