There appears to be major problems getting accurate tail numbers for Southwest flights for the last several weeks. Everything seems to get corrected exactly 1 hour before scheduled departure time. But until then, it’s all messed up.
You are seeing that because that is what our upstream data provider is sending us. These will automatically update as we receive newer information. We are checking with the provider of this data to see if there is anything that can be done to address this particular issue with SWA.
In our experience, airline tail assignments can be unreliable, particularly in advance, even when we get them reported directly from the airline. But this will vary by airline.