Yet hopes that air security would meet an ambitious goal envisioned by a post-9/11 law haven't been realized. The Transportation Security Administration (TSA), created in November 2001 to overhaul a disastrous safety system, should be hitting its stride by now. Instead, it is struggling with multiple challenges, from electronically screening all checked bags for explosives to plugging holes in porous airport perimeters.

While the TSA has contributed to its problems, some blame goes to constraints wrought by the same people professing to want a better system.

Tight budgets, leadership changes and battles with critics in Congress have undermined the agency's efforts to tackle its vast security problems. The result is that all taxpayers are footing a higher bill for security than lawmakers intended when they created the TSA. And travelers continue to face security risks that the agency had promised to fix by now.

Hamstringing the agency are:

•Budget constraints. Congress has made the TSA's challenging security goals even tougher by coupling them with unrealistic deadlines and inadequate financing. Ignoring estimates from its own budget experts, Congress pretended that a $2.50 fee it imposed on each passenger would cover security upgrades. Given a huge drop in air travel, receipts from the fees haven't come close. In the last fiscal year, they brought in just $1.9 billion out of a TSA budget of $5.8 billion, according to congressional staffers. That has forced all taxpayers to make up the difference. And it illustrates how lawmakers' shortsighted estimates have contributed to the TSA failures they complain about.

•Unfocused objectives. After 9/11, Congress ordered the TSA to scan all checked baggage by the end of 2002. At the time, it expected high-tech detection machines would do the job. But lawmakers failed to anticipate how much equipment would be needed, whether it could be produced in time and how much it would cost to install it at the nation's more than 440 commercial airports. When too few of the huge scanners were produced, purchased and installed in time, the TSA fell back on supplementing the sophisticated machines with less-thorough detectors.

In the same law, Congress ordered a screening system for air cargo and tighter security for airport perimeters, but it neglected to set deadlines for either critical task. Little has been done as a result, leaving passengers vulnerable to attacks aimed at these unprotected targets.

•Damaging doubts. Rep. John Mica, R-Fla., who chairs the House aviation subcommittee, wants airport screening returned to the same private sector that bungled it on Sept. 11, 2001. Mica lost that battle when

 Congress voted to hand over this critical job to a new federal workforce under the TSA. The private firms had proved to be low-wage operations plagued with poor morale, high turnover and shoddy work by screeners who repeatedly failed to spot dangerous objects. The Swiss-cheese security they provided was exploited by the 19 hijackers on 9/11. Mica's focus on dismantling one of the TSA's central functions takes away energy that could be directed at improving the troubled agency.

Mica argues that when air security is at stake, the "government will never get it right." He points to a recent classified report of guns, knives and other weapons slipping past screeners. Yet, private firms had a long, sorry history of overlooking dangerous weapons and making bad hires as screeners, such as convicted felons.

Certainly, the TSA's actions have made it an easy target for Congress to criticize. It has granted wasteful private contracts for recruiting and hiring screeners, tried to cover budget shortfalls by scrimping on a vital air marshal program and failed to take meaningful steps to secure cargo loaded in the bellies of passenger jets. But scuttling the agency is not the answer.

A better solution would be for Congress to set realistic priorities for the TSA, provide money to pay for them and hold the agency accountable for meeting those goals. In a report this month, the General Accounting Office (news - web sites), Congress' investigative arm, said that testing the TSA's effectiveness is a key part of enhancing air security. Pilot programs that continue using private screeners are in place at five U.S. airports. Evaluating their performance against the TSA's is a sensible way to tailor future air security.