I had this down as a 4* rating from memory, yet upon rewatch I see no reason for it to be upped, even if ever so slightly. Surely, this is one of the best one-shot original sci-fi thrillers of the past 20 or so years. The slow reveal of what Source Code actually is, Jake Gyllenhaal's fantastic performance, the believable underlying threat and the murder-mystery aspect all combine and complement each other so well. Save for a couple of forgivable plot holes (come on, let's give them some artistic license), I think the ending sequence is beautiful. The human moments that have been woven neatly in this mostly action-thriller are what sets it aside from similar but forgettable movies like The Tomorrow War, which compromise on the necessity for genuine, believable human beings.

Does this come under my sub-genre appreciation of "time-loops"? I'm going to go with yes.