Lying awake at night, the speaker hears the usual quiet sounds: cars on a highway, the wind. Then a plane cuts through the silence, and what could be an annoyance turns out to be a welcome surprise. The speaker admits to missing that noise during a few sleepless nights without it.
From there the poem makes a quiet leap. The plane, which arrives briefly and then disappears over the horizon, reminds the speaker of people. We carry on with our lives and forget those who once mattered, until we see them again and our eyes light up and the missing comes flooding back. The speaker also adds a reminder that those people have lives of their own, and that sooner or later they drift away, leaving "a hole / And nostalgia."
The mood is calm, wistful and a little lonely. The plain, conversational language ("I'll be honest," "it kinda hit me") makes it feel like a private thought spoken out loud in the dark.