Those familiar with the new departure clearance phrase “climb via” say it continues to cause confusion among flight crews and air traffic controllers. “Only 5, maybe 10 percent of pilots are using the appropriate climb via phraseology,” said Rich Boll, who chairs the Airspace, ATC and Flight Technologies Working Group of the NBAA Access Committee. Climb via clearances are based on SID procedures and were first used on air traffic control frequencies on April 3. When receiving such a clearance, flight crews are supposed to comply with lateral, vertical and speed restrictions published in the SID. Those provisions are designed to increase the efficiency of communications between ATC and flight crews.