Major airlines, somewhat like chastened students writing "I will be good" hundreds of times on a blackboard, yesterday gave the federal government updated plans promising to be kind to their customers.

Each airline's plan followed the "Customer First" guidelines hashed out earlier between the airlines, members of Congress and the Clinton administration. The carriers promised to be more open and prompt in telling customers when flights are delayed, canceled or oversold, and to fully disclose their policies and rules.

In most cases, the plans were vague on exactly how the airlines would provide passengers with better information. In many cases, gate agents themselves do not have access to accurate information, or must consult numerous computer programs to get it. A major exception was United Airlines, which promised to implement a new "one-stop" information system to give gate agents immediate access to all levels of flight information. In addition, United said it would deploy mobile computer work stations called "Chariots" to allow several extra gate agents to help at crowded gates, and would deploy 600 hand-held devices to give customers on-the-spot real-time information on the location of their lost baggage.

Many of the new policies are basically old policies that the airlines now promise to enforce, but a few small changes potentially will have a major impact on passengers. For instance, most of the plans will now allow passengers to receive a refund on "nonrefundable" tickets provided the reservation is canceled within 24 hours of making it.

All the airlines also promise to offer callers the lowest fare available, to do better in handling customer complaints--often with new toll-free numbers--to promptly search out and deliver lost baggage, and to ask the Transportation Department to double the maximum compensation for lost baggage to $2,500.

The plans grew out of public dissatisfaction with airline service, as expressed by a raft of proposed legislation that congressional sponsors generally called a "passenger bill of rights." Rather than pass new legislation, most of the sponsors agreed to let the airlines work out their own plans under the umbrella of the Air Transport Association's "Customers First" plan.

Sen. Ron Wyden (D-Ore.), however, described the plans as "legalistic gobbledygook." On Tuesday, he released reports from the General Accounting Office and the Congressional Research Service that generally said the plans are unenforceable, although the GAO report said the Transportation Department could bring "unfair and deceptive trade practice" charges against airlines that broke their promises.

The Senate yesterday passed Wyden amendments to an appropriations bill requiring a Transportation Department investigation of airline overbooking and deceptive competition practices. But one Wyden amendment--which would have specifically defined as an unfair trade practice the failure to disclose an overbooked flight or to offer a passenger the lowest fare available--was watered down to a "sense of the Senate" resolution. Presumably that would end special fares available only on the Internet, but a sense of the Senate resolution does not have the force of law.

The defining event that led to congressional outrage was the stranding of hundreds of Northwest Airlines passengers aboard aircraft for up to eight hours during a blizzard in Detroit. All of the plans promised to make "every reasonable effort" to provide food, water and restroom facilities to stranded passengers and to develop contingency plans to get the passengers into the terminal.

Northwest's plan would give each aircraft captain the authority to implement a new "event recovery plan" if an inbound aircraft has been held out of a gate for an hour or more, and give the captain discretion to determine when the wait for outbound flights has become excessive.

CAPTION: Northwest Airlines passengers try to relax during a seven-hour wait on a Detroit runway Jan. 3.