SYDNEY -- On two recent occasions, a pair of Sukhoi Su-30 fighters have taken off from their base near the old Indonesian trading port of Makassar and flown far across the Indonesian archipelago to intercept unidentified aircraft. One of the mystery planes, a light aircraft being ferried from Darwin in northern Australia to its new owners in the Philippines, was chased a long distance before being forced to land in Manado, a city on the Indonesian island of Sulawesi.