Nearly a decade ago, 14 of the country’s major airlines signed an Airline Customer Service Commitment that outlined what they would improve in areas such as handling delays and baggage. Many of the commitments are not being met, the Department of Transportation’s inspector general recently concluded. That, coupled with passengers being held in planes for up to 11 hours on the tarmac during last week’s blizzard, has prompted a renewed debate of an Airline Passenger Bill of Rights in Congress. Before lawmakers mandate customer service, they should determine if problems like last week’s, which predominantly affected low-cost carrier JetBlue, are widespread.

If they are isolated, Congress should let consumers decide whether low fares are worth the risk of terrible customer service. If they are widespread, there may be other remedies, such as better enforcement of existing airline consumer protection provisions.

The founder and chief executive of JetBlue Airways, David Neeleman, told The New York Times he was “humiliated and mortified” by his airline’s performance during and after the Valentine’s Day storm that snarled air traffic along the East Coast. Nine JetBlue planes full of passengers sat for at least six hours at New York’s John F. Kennedy Airport. One plane held passengers for 11 hours.

Mr. Neeleman said his company’s low-cost operating structure failed with too few reservation agents, many of whom work out of their homes, available to answer calls and pilots and flight attendants stranded. JetBlue also underestimated the severity of the storm and did not preventively cancel flights as other airlines did. To regroup, the airline continued to cancel all of its flights out of some cities, including Portland, on Monday, nearly a week after the storm.

Mr. Neeleman, who acknowledged passengers would choose other airlines if problems persisted, said JetBlue would enact its own customer bill of rights soon.

That’s a good promise, but one that airlines have made before. After similar problems in 1999, the airlines pledged to improve the situation in lieu congressional action. The result was the June 1999 customer service commitment, which promised better information about flight delays, prompt baggage handling and attention to passenger needs and cooperation to make gates available during on-aircraft delays. JetBlue, which began in 1999, did not sign the commitment.

The DOT inspector general’s November report found that since 2000, the percentage of delayed flights has decreased from 27 percent to 22 percent in 2005. The average delay remains about 50 minutes. In 2000, flight problems accounted for 40 percent of customer complaints. That dropped to 26 percent in 2005.

However, in many instances, airlines still do not provide adequate or up-to-date information on why and how long flights will be delayed. For 2005, the IG identified more than 15,000 flight numbers (representing more than 200,000 individual flights) that were chronically delayed, meaning they were canceled or more than 30 minutes late at least 40 percent of the time. The DOT can take enforcement action against airlines that consistently advertise flight schedules that are unrealistic, regardless of the reason.

Customers taking their business elsewhere, coupled with government sanctions where warranted, is likely to be more effective than an unenforceable bill of rights.