From the restless throat of Anak Krakatau — a name that carries centuries of geological memory — volcanic ash drifted northward into the skies above Jakarta on Sunday, compelling the city's main airport to silence its runways until the air could be trusted again. Thirty-three flights, including several Singapore Airlines services, were suspended or rescheduled as the eruption that began Friday evening continued to assert nature's authority over human timetables. Authorities moved quickly to distinguish between the disruption that was real — ash in the air, engines at risk — and the catastrophe