So apparently 決行-けっこう (to carry out) and 欠航-けっこう (cancelled) are pronounced the same way? Or does one of them have a different pitch accent pattern? At least Google translate pronounced them the same. This seems problematic for a situation like the following, since you can't tell from context: https://youtu.be/J2vVPpbEdH0?t=21
決行 and 欠航 are pronounced the same, but you can tell which is used from the context. Simply, 決行 is not a word used in a situation like the one in that video. Note that the person on the right is supposed to be a traveler who doesn't speak Japanese like a native speaker.
決行 means holding a public/social event or carrying out a plan/operation determinedly despite some obstacle (typically bad weather). Here "event" includes a live concert, a sport game, a competition, a strike action, a military operation, and so on, but not a departure of a ferry/airplane.