Blast analysis, which looks at how a building withstands an explosion, has become a routine part of airport design, said Tom Darmody, senior vice president of aviation and transportation for the design firm HOK. “For the most part, people weren’t even thinking about this till after 9/11,” said Andy Bell, vice president of planning at the Dallas/Fort Worth airport.

Planners generally use bollards or cement piers to keep possible bomb-laden cars at least 20 ft from a building’s support beams, said Dick Marchi, a senior adviser with Airports Council International-North America. “The real fear is that somebody will bring a building down,” Marchi said. “Turns out with blast protection, a relatively small distance (away) does an awful lot of good.”

Airports have spread out the cost of these upgrades using bond revenue, rent hikes and parking garage money, among other sources of income. Still, some of the expense filters down in the form of higher prices for a cup of coffee or a parking space. “The passenger ultimately pays for everything,” Marchi said.

Planners at Indianapolis terminal also spent $24 million to build an inline baggage screening system beneath the terminal’s main floor. The system includes about a mile of conveyor belts that feed luggage through scanners, which compare bag contents with properties found in explosives. Security personnel will keep watch from a nearby room, and they’ll be able to quickly divert any suspicious bags.