Updated

The government has spent millions since Sept. 11, 2001, to develop a system to ensure terrorists don't board planes. But they still can't get it right — and shouldn't do any more work on it until they do, an oversight panel said Friday.

The project, called Secure Flight (search), sounds simple: Match passenger names against terrorist watch lists.

But it isn't so simple. Secure Flight and its predecessor, CAPPS II (search), ran into repeated trouble since the Transportation Security Administration started work on them shortly after the Sept. 11 terrorist attacks. Government auditors gave the project failing grades — twice — and rebuked its authors for secretly obtaining personal information about airline passengers and then not telling the truth about it.

"They didn't know what they were doing," said James Dempsey, a member of the oversight panel and executive director of the Center for Democracy and Technology.

A big part of the problem is that many people have the same or similar names. For example, Sen. Edward Kennedy, D-Mass., was told he couldn't board a plane because his name matched that of a member of the Irish Republican Army.

The TSA hoped to remedy that problem by getting more information about passengers to verify their identities.

Critics who viewed Secure Flight as a secret project to spy on Americans stalled its progress, but the authors of Friday's report said the project's problems run deeper than that.

"It's not a privacy problem," Dempsey said. "It's a mission, goals and methods problem."

The oversight panel said it wasn't sure Secure Flight could ever work.

"We cannot assess whether even the general goal of evaluating passengers for the risk they represent to aviation security is a realistic or feasible one or how TSA proposes to achieve it," the report said.

The TSA appointed security and privacy experts to the oversight panel.

"We asked for the criticism, we welcome it, and we'll take it under consideration as we move towards implementation," said TSA spokeswoman Amy von Walter. "We think that's good government, and we're confident the public will agree."

The TSA has decided not to include one of the program's most controversial elements: using commercial data to help verify passengers' identity before they're matched against the lists.

Von Walter said the Secure Flight oversight panel had nothing to do with that decision.

"We recognize there were privacy concerns about its use so we decided against it for this initial program phase," she said.

But Dempsey said commercial data wasn't even useful in verifying peoples' identity.

The report noted that the TSA frequently shifted its definition of what information it was collecting for what reason.

Over the course of its development, the TSA said the system would only look for terrorists, then said it would also look for violent criminals. The TSA also said it would only be used to match names against terrorist watch lists, then that it would be used for the far broader purpose of identifying terrorist sleeper cells.

The report also noted that the oversight panel wasn't told what kind of hardware and software would be used or how airlines would transfer passenger information to the government.