New and renovated airports have poured millions of dollars into safety upgrades since the September 11 terrorist attacks, working advice from explosives experts into design plans that encompass everything from the most secure place for parking garages to more efficient security checkpoints.

“We haven’t had to dig a moat around the terminal or anything,” said Jay McQueen, deputy project director for the Indianapolis terminal. “It’s been an incremental set of changes to help make everything more secure.”

The 9/11 attacks, in which hijackers seized control of airliners leaving from Boston, Newark and Washington, triggered a massive re-examination of airport security. Passengers saw the formation of the US Transportation Security Administration shortly after the attacks, and they’ve since become used to spending more time in security checkpoints having their shoes x-rayed and carrying only limited amounts of liquids.

But many other upgrades fly beneath their radar. “We like to say around here that the best kind of security is the security that you can’t see,” said Ken Capps, vice president of public affairs for the Dallas/Fort Worth International Airport, which opened a new international terminal in 2005.

In Indianapolis, those steps include windows that will fold like a drape when broken rather than exploding into shards of flying glass and a 240-ft-wide strip of lawn that will separate the front entrance of the new terminal from its five-storey parking garage. The grassy median isn’t for pastoral effect. It’s the product of a federal mandate requiring all buildings that hold cars be kept at least 300 ft from an airport terminal.

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.