The Terrorism Research Center has reduced the Terror Alert Level to yellow. The Bush administration lowered the national terror warning level Friday as Homeland Security Secretary Tom Ridge said that an urgent threat had passed. However, the airline industry remained at high alert. “I know we are all thankful that nothing happened,” said Ridge, announcing the lowering of the threat level for most of the country at a news conference. Ridge acknowledged that certain locations and sectors of the economy, which he did not identify, will keep their security posture at the orange level. But a U.S. official speaking on condition of anonymity had said earlier that airports and airlines will keep their high alert status. During heightened alerts, airports are asked to restrict parking near terminals if necessary, increase law enforcement patrols of terminals and perimeters and conduct random checks of vehicles on airport roadways. The alert level went from orange, signifying a high threat of terrorist attacks, to yellow, signifying an elevated threat. The conclusion of the holidays — and the large gatherings that go with them, played a role in the decision to lower the threat level, Ridge said.