Southwest Airlines’ ambitious fleetwide implementation of required navigation performance (RNP) operations is making slow progress. Since initiating flights in January using the precision approach procedures to save track miles and fuel, the airline’s use of RNP represents just 1 percent of its daily operations, said Capt. David Newton, Southwest senior manager of airspace.

Despite accepted benefits in saving fuel, mitigating aircraft noise and enabling approaches into geographically challenging areas, RNP “is just not the cultural norm,” Newton said. U.S. terminal airspace remains dependent on instrument landing system (ILS) approaches, and the air traffic controllers haven’t received the equipment and training to handle mixed fleets with RNP-capable aircraft.

Newton reported on Southwest’s progress September 27 at the GE Aviation Performance-Based Navigation (PBN) Summit in Seattle. RNP is a subset of PBN, considered the navigation component underpinning the Next Generation Air Transportation System in the U.S. Although carriers such as Alaska Airlines, WestJet and Qantas have flown RNP approaches for some time, Southwest in 2008 announced an industry-leading program to equip its fleet of more than 500 Boeing 737 classics and NGs for the capability. The six-year, $175 million effort involves training 6,000 pilots to fly precision approaches and designing new procedures at the 73 airports in Southwest’s network. The network grew by 30 more airports with Southwest’s acquisition of AirTran Airways in May.

As of January 11, Newton said, Southwest had deployed 335 RNP-capable aircraft and run its pilots through 32 hours of ground school and 12 hours of simulator time. As of September 26, the airline had flown 5,807 RNP Authorization Required (RNP AR) approaches, Newton said–a remark that initially drew applause. “The bad news is those RNP AR operations are approximately 1 percent of our daily operations,” he said. “We have 3,400 flights a day.”

Southwest made good progress initially, flying 1,400 RNP AR approaches in the first 20 days since beginning the procedures in January. Since then, the operations have slowed to fewer than 400 a month, in part because controllers usually refuse permission to fly the approaches. Meanwhile, Southwest has developed RNP AR approaches at just 16 airports. “It’s going to take a long time at this rate to build those [approaches] out,” Newton said. “In meeting our benefit case, we have to not only fly them efficiently, we have to have them at all our airports and we have to fly them more often.”