A long dormant volcano has erupted in Eritrea, spewing a huge ash cloud across the Horn of Africa and threatening air travel. The Volcanic Ash Advisory Center, which monitors volcanoes for the aviation industry, says the Dubbi volcano began erupting late Sunday. Germany's Lufthansa said it cancelled a flight out of the Eritrean capital, Asmara, and a flight into Addis Ababa from Frankfurt. U.S. officials said they had been told Ethiopia was considering shutting down Addis Ababa's main international airport due to the impending ash cloud. Satellite images suggest Sudanese airspace could also be impacted.