I feel like I keep having to rename this series of moments. First was to make it a little more punny, but now it’s because I’m recognizing that the Best Destiel "lines” are often unspoken, they’re more “moments” so here we go...
In this moment, Jack is telling Cas and Sam that he and Dean are off on a trip, they don’t say where they’re going or what they’re doing, just that they’re going out for a ride in Baby.
Now, keeping in mind my personal perspective that Cas is Jack’s dad and Dean is Jack’s step-dad (And Sam is the most supportive uncle ever!), this moment carries much more weight, imo.
If you look at the first frame, Cas is clearly looking right at Jack as Jack tells him about their plans to go out. Dadstiel clearly does not think this is the greatest idea, but instead of yelling at his son, he turns to his husband to get some answers. It’s just a shift in direction with his eyes, but he has very specifically shifted his glance to Dean in this moment. He is not asking Jack where they are going, he is asking Dean because he is trying to get across his disapproval without stating it out loud.
I watched this moment a half-dozen times and it made me so happy to see it happen. It could be subtle, because there is no cut from Jack to Dean here, it’s ONLY in the shift of Castiel’s eyes that we get the unspoken questions from one husband to another, one dad to another. And that is why this moment stood out to me as the best Destiel line of the episode.