It may have been relating to the Pilot Operating Handbook procedures the Airlines' Air Operators Certificate requires. They still have the means to manually ca

It may have been relating to the Pilot Operating Handbook procedures the Airlines' Air Operators Certificate requires. They still have the means to manually calculate the weight/balance etc. Some (most?) airlines require the pilots to do a manual cross-check worksheet of the fuel, weight/balance and a few other safety of flight items, before they take-off. This helps avoids mistakes like over-rotation on takeoff etc. One particularly amusing case was in a 767, where the Captain handed a copy of the worksheet to a young girl who loved math problems, and was travelling in first class as a VIP. The young girl found a mathematical error in the worksheet. It turned out the flight computer had the fuel CG incorrect by 2-3% in certain cases, and both were incorrect. A quick call to Boeing, and 20 minutes later, fuel transferred and the flight proceeded. I suspect the Southwest aircraft returning to the gate, was a procedural abort, than a safely-of-flight issue.