INDIANAPOLIS — Nine bulky luggage scanners worth $1 million each wait silently beneath the new terminal, poised to check for explosives at a combined rate of 3,600 bags an hour.

Concrete bollards guard the main doors. Blast-resistant glass fills the front windows of the $1.1 billion terminal at Indianapolis International Airport, which will open this fall.

New and renovated airports have poured millions of dollars into safety upgrades since the Sept. 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 Sept. 11 attacks triggered a massive re-examination of airport security. Passengers saw the formation of the U.S. 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 Dallas/Fort Worth International Airport, which opened a new international terminal in 2005.

PASSENGERS FOOT BILL

In Indianapolis, those steps include the bollards, windows that will fold like a drape when broken rather than exploding into shards of flying glass, and a 240-foot-wide strip of lawn that will separate the front entrance of the new terminal from its five-story parking garage.

The grassy median, which will be planted between the garage and a road leading up to the terminal, isn't for pastoral effect. It's the product of a federal mandate requiring all buildings that hold cars be kept at least 300 feet 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 feet to 30 feet 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.

The Indianapolis terminal is one of the first airports designed and built since Sept. 11. Planners more than doubled the space provided for security equipment compared with the current airport. They added a room for isolating international travelers suspected of carrying a contagious disease.

They 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.

MAKING FLIERS HAPPIER

Since the government now requires all baggage to be checked for explosives, the Transportation Security Administration provided the scanners for Indianapolis. Previously, only luggage on international flights had to be scanned.

Dallas/Fort Worth plans a similar baggage screening system for its five terminals. Bell expects to spend about $140 million on it by the time it's finished in 2010.

Construction started on that airport's new international terminal shortly before the 2001 attacks. Planners adjusted their design to add $47 million in security upgrades.

They fortified walls with more steel and concrete, and they set up a separate road for deliveries. Drivers must pass a security checkpoint to get near the terminal. Shipments are then dropped at a central location and screened before they reach the vendor.

"This is really the trend of the future," Bell said. "Everybody would be basically prearranging this so there wouldn't be any strange beer truck that comes out of nowhere."

Airports also hope to boost security by making passengers happier about the checkpoint process.

Indianapolis will use natural light to help improve the mood around its two checkpoints, and it plans to install monitors that tell passengers how long it takes to pass through checkpoints.

The Dallas/Fort Worth airport, meanwhile, plans to use video displays and recorded messages to direct passengers in a less irritating manner.

"In the past, the town crier TSA guy would, every five minutes, look up and start yelling at everybody to take out your liquids," Bell said.

Bell also wants to set up parallel tables before the checkpoints so more people can remove their shoes and wallets for scanning. That will tame checkpoint waits and keep passengers calm, which makes it easier to spot potential problems.

"If everybody's irritated and cussing," Bell said, "it's hard to tell who might be a person of interest."