In 1998, people showed up with insufficient or no food, and complained when the Dome served them hot dogs and orange juice. When kept from leaving after the storm because of a curfew, shouting matches erupted with security and police. Some occupants hauled off televisions and furniture.

"I'd say 99 percent of the people were fine," Thornton said. "But we didn't have enough security people to handle the crowd and prevent problems."

The Superdome can withstand most catastrophes; the roof is built to stand up to 200 mph wind and even deep flood water wouldn't reach the second level 35 feet from the ground.

There are potential problems nonetheless. Although the building has its own generators, they would not provide lights or air conditioning for the entire area if electricity went out. Nor would pumps providing water to second-level bathrooms function.

Just as during Georges, the Dome has only a small work crew for Ivan, which means providing security and services gets even harder, Thornton said.

"The office of Emergency Preparedness and the city decided that the Dome would not be operated as a shelter," he said. "That means we are not equipped as one."

The city previously provided shelters for those unable to leave when storms threaten. Now, the Red Cross will not set up shelters for a storm larger than a Category 2, saying New Orleans -- much of which is below sea level -- is not safe in bigger storms. Because of that, the city concentrates on evacuation first.

From a planning standpoint, Nagin said he did not regret keeping the Superdome from use until the last minute. "As far as an empathy standpoint," he conceded, "we could have moved a little quicker."