From the Distancia site:
"Adicionalmente, sólo boletos con tarifas "Y" y "C" son válidos para acumular millas en vuelos domésticos dentro de Perú." Roughly translated this means: Only flights booked in "Y" and "C" class are eligable for mileage accumulation on domestic flights in Peru. A Distancia representative advised me I would acquire mileage with a flight booked in class W and I later found this to not be true. Fortunately it only cost me twenty dollars to upgrade the ticket but it could have cost 500,000 miles. Be very careful and if the fare has an exclusive limitation as this one does; heed the written warning.