If a jumbo jet dropped out of the sky every other day, you can bet all your frequent-flier miles that the nation's leaders would leap into action with a plan to safeguard air travelers.

So what's taken Washington policymakers so long to deal with a problem that contributes to as many as 98,000 deaths nationally each year?

The problem is medical errors.

The scale of the problem has been known at least since 1999, when a landmark Institute of Medicine study cited that number as the upper range of how many people are killed by medical errors annually.

Yet Congress and two presidential administrations took nearly six years to agree - just last week - on what, even now, is a minimalist plan to limit preventable health-care errors.

On Friday, President Bush signed into law a national system for reporting and analyzing medical errors. Under a voluntary, no-fault arrangement, health-care officials will report mistakes to patient-safety groups. Those groups will analyze the data and suggest safeguards.

By all means, celebrate the fact that something has been done. No one should pretend, though, that this voluntary system is going to yield all the data needed to prevent errors.

Practitioners and hospitals have been assured confidentiality. That's necessary, given the fear that public candor about errors will only feed medical malpractice lawsuits.

Having guaranteed that the data could not be used to hammer people in court, though, Congress should have made the reporting mandatory. That's already the law in nearly two dozen states, including Pennsylvania and New Jersey.

Without a federal mandate, the reporting likely will range from spotty to nonexistent. If so, the promise of improving patient safety will be hollow.

A mandatory reporting system was proposed during the final year of Bill Clinton's presidency. It went nowhere, in large part due to opposition from hospital and physician trade groups.

Regional volunteer initiatives to reduce medical errors are commendable. The Philadelphia area boasts one of the best. Since 2002, its 49 hospitals have been sharing data to develop best practices for patient safety. But such efforts are no substitute for a coordinated national attack on medical errors, one which accumulates enough data to detect not just national trends, but problematic regional variations.

Patients could lose out twice on this voluntary system. Its gaps might slow the development of safety improvements. And its existence will clearly be used by some in Congress to justify limiting injured patients' recourse to the legal system.

How so? The House has approved caps on court awards for pain and suffering due to malpractice. Some backers of the reporting bill clearly want to exploit it as a pretext for the Senate to approve caps as well. Caps make it harder for lower-income patients in particular to find lawyers to take their cases.

As much as doctors loathe the idea, the legal system still acts as a needed check against preventable errors. The system has flaws that should be fixed carefully, not with a partisan hammer.

The new patient-safety reporting system is no cure-all for medical errors, but it could help if it attracts robust compliance. Health-care officials should make this their mantra: Report and learn, report and learn.