For years, supply chain management has been built on one core premise: the less inventory, the better.

At first glance, the September 11 attack on America appeared to challenge that premise. Planes were grounded, international borders closed, and transportation ground to a halt.

As a result, inventory intended for The Gap, Banana Republic, and Old Navy stores was stuck in port.

A shipment of toilets destined for a major plumbing supply distributor was stalled at the Mexican border.

With 30-mile plus traffic jams at the Canadian border, Ford was forced to shut down five assembly plants for a week after the automaker ran short of critical parts.

At first, it appeared that the lean supply chain was another casualty of the attack on America. Some thought that companies were moving from just-in-time to just-in-case inventory levels.

But more than one month after the attack that does not appear to be the case.

In fact, inventory was once again flowing through the Gap's distribution centers, and Ford's inventory levels were lean and mean by September 18.

"We've said all along that lean manufacturing and JIT are the way of the future," says Ed Lewis, a spokesman at Ford. "We have no plans to back away from either initiative.

By October, shippers like the UPS Logistics Group, the supply chain arm of the parcel carrier, were reporting that even international shipments were flowing close to normal. "We're still seeing some slowdowns at the northbound Mexican border," says Lynnette McIntire, spokesperson for UPS Logistics Group, "but less trouble at the Canadian border. There are some slight delays due to security checks in Europe and Asia but nothing troublesome."

According to Jim Apple, Jr., a partner with the Progress Group, Atlanta, Ga., just-in-time seems to be firmly in place. "There may be a short-term build up of inventory," he says, "but in these tough times there's just too much pressure to cut costs to carry just-in-case inventory."

Still, the events of September 11 are having an impact on how supply chain professionals think about their supply chains going forward.

"Immediately following those events, I got calls from senior management at several Fortune 500 companies," says Dick Metzler, CEO of APL Logistics, a third party logistics provider in Oakland, Ca. "They wanted to know what kind of contingency plans we could put in place to make sure they weren't caught short again."

One executive asked Metzler to create a "Def Con One" contingency plan covering events like the closing of the Suez or Panama canals, and the shut down of the air cargo transportation industry.

Going forward there are several steps a company can take to maintain lean inventories and a responsive supply chain.

One is to look at where you store your inventory. "Some of our customers used to store all their inventory in the U.S. and relied on overnight shipments to Asia or Europe," says McIntire of UPS Logistics Group. "Now, they're asking us to redeploy some of that stock to get closer to the customer."

Another approach is to shore up your materials handling systems. Many facilities today are geared around cross-docking or flowing inventory through the distribution center. "If we do see increases in buffer stock, materials handling systems are going to be a must to reduce handling and increase productivity," says John Splude, CEO of HK Systems.

Yet another option is to optimize those things you can control. "Now is the time to review all of your shipping modes, how reliable they are, and how much control you have over them," says Louis J. Cerny, vice president, Sedlak Management, Richfield, Ohio. "You can't control the U.S. Postal Service, but you can control where and how your merchandise gets into the system."

Finally, Steve Banker, a supply chain analyst with ARC Advisory Group, Dedham, Ma., urges companies to invest in new supply chain software solutions. His list includes: global transportation management systems with the functionality to manage cross-border shipments; supply chain planning solutions that allow strategic planning and what-if scenarios; supply chain visibility solutions that track shipments down to the stock keeping unit level throughout the supply chain; and event management solutions that notify users when critical milestones have been missed.

Third party logistics providers like UPS Logistics Group and APL are already using those systems to help their customers respond during the crisis.

Ultimately, taking steps to re-examine how our supply chains work might benefit business in the long run - a just-in-case approach to insure the survival of just-in-time supply chain management.

"One of the things that's always been true is that businesses design and implement supply chain models and then don't look at them again. They become outdated because we're not paying attention," says Steve Banker. "A certain amount of re-assessment is a healthy thing."