The Defense Department is the world's biggest purchaser of airline tickets -- so the Pentagon bought its own online booking system called the "defense travel system," which was supposed to save money on travel agents and paperwork.
The defense travel system was also supposed to buy only the cheapest seats. But many in Congress say the system is a disaster -- four years behind schedule and $200 million over budget.
"It will take 200 years to ever pay back the cost of this contract in terms of that savings," Sen. Tom Coburn, R-Okla., told ABC News, "especially when you consider they're not getting the best price."
Four years ago, the Pentagon's inspector general recommended killing the defense travel system altogether, but it survived. Investigators say 70 percent of Pentagon travelers refuse to use DTS because of faulty software or because they believe they can get a better price elsewhere.
"In many cases," said Tom Schatz of the private group Citizens Against Government Waste, "they're simply finding it easier to pick up the phone and call the travel agent and say, 'I'd like to go from here to there. Can you do this for me?' "
In fact, critics say the Pentagon could get cheaper air fares simply by using discount online travel sites that many bargain-hunters use -- such as Travelocity or Expedia.
But Northrup Grumman, the company that devised the defense travel system for the Pentagon, said that's not true. Darryl Fraser of Northrup Grumman told ABC News the system will be up to speed sometime this fall.
"This is a program that the American taxpayer [and] the Department of Defense can be proud of," he said. "It is actually being deployed. It is being used, and it is going to save the Department of Defense money."
The company says part of the problem was that some Defense employees were reluctant to use DTS, and were more comfortable using the old travel system. That has changed, said the company, as more workers have gradually become more familiar with the new system and realized it is better.