The data I'm using comes from MIT's Airline Data Project. I footnoted that on the chart where I referred to Delta pilots flying 30% more block hours, on average, than SWA pilots. But it may have been too small to read if viewed on a mobile device. Here is exactly what the footnote said: "Using latest data available (2018) for both SWA and Delta Airlines from the "Airline Data Project." Massachusetts Institute of Technology Global Airline Industry Program, http://web.mit.edu/airlinedata/www/default.html".

2018 is currently the latest data published for Delta by the Airline Data Project. So, I compared SWA's 2018 "Block Hours Per Employee Per Month - Pilots & Co-Pilots (note: Includes Flight Engineers where applicable)" which was 53.1 block hours to the same 2018 figure for Delta, which was 40.6 block hours. The difference is 30.8%.