And I mean close the airport during the non-peak times—not close the airport forever.

I suspect this is scheduled during non-peak time for the airport to ensure resources are available during peak times. The only other alternative would be to close the airport entirely.

This means this still has more ATC services than a typical non-towered airport.

There’s a NOTAM for it. Most airports in the US are untowered, but this is interesting because it’s an airport in Class C airspace. For a part-time tower at a Class D airport, the airspace typically reverts to Class E. In this case, SoCal Approach is handling Class C services.

I don’t know Hoover, but his analysis is normally really spot-on.

Validate the csv file before doing anything. Check if it has quoted fields, extra fields, missing fields, and if any of those things are expected. Even something as simple as “wc -l” can help make sure you have the number of records you’re expecting.

Sailors? Hmph. This would definitely be a conversion aircraft pilots would use.