LOS ANGELES -- Construction crews are knocking down walls and reconfiguring electrical wiring at Los Angeles International Airport to accommodate hundreds of bomb-detection machines that are to arrive next month, in one of the most daunting airport security improvement projects in decades.

Officials at the fifth-busiest airport in the world said they will meet a Dec. 31 deadline to use the machines to screen all checked luggage for explosives. That contrasts sharply with dozens of other airports, including Dulles International and Baltimore-Washington International, where officials said the deadline is unreasonable.

The deadline was imposed by Congress last year as part of an airport security measure enacted after the hijackings on Sept. 11, 2001. Dozens of airports have been lobbying Congress to delay the requirement for at least another year.

The Transportation Security Administration, the federal agency in charge of airport security, used Los Angeles as an example of how airports could comply with the law if less energy were spent fighting it. If airport officials in Los Angeles "had the attitude of -- it's just too hard -- it would have been extremely difficult to have an airport of this size do something," said David Stone, the TSA's security director here.

Los Angeles airport officials said that to meet the deadline, they had to spend $4 million to hire planning consultants, and they have no assurance that the TSA will reimburse them. Airport and airline officials had to spend a lot of time negotiating with the TSA about the best way to screen the luggage.

Despite the time and money the effort entailed, airport officials said they never doubted that they could have the bomb detection machines in place by the deadline. "It's a moral obligation that we meet these deadlines," said Lydia H. Kennard, executive director of the agency that runs the airport.

One reason for Los Angeles International's push to comply with the law is that it was selected by terrorists in 2000 for an attack, which was thwarted, and that three of the four planes hijacked on Sept. 11 were bound for Los Angeles.

Bullet holes from a fatal shooting July 4 at the airport's El Al ticket counter here have been patched up, but passengers looking closely can see where they were.

"What price tag is there to put on the safety and security of the traveling public?" Kennard said. "Four million dollars is a very small price to pay for achieving that next level of security."

Airport directors opposed to the deadline say they too want better security but that the federal government should pay for it. "This is not our deadline, it is TSA's deadline," James Wilding, director of Reagan National and Dulles airports, has said several times over the past few months. Wilding has said he expects Reagan National Airport, which handles fewer passengers and where several bomb-detecting machines already have been installed, to meet the deadline.

The TSA, created after the terrorist hijackings, was charged with overseeing the security improvements. Airport officials said the new agency took a long time to draw up plans and that those airports that tried to move ahead, hiring their own consultants, often ran into roadblocks from the federal government. For example, Denver hired a consultant to prepare plans, which were later rejected by the TSA because they involved the use of technology not approved by the Federal Aviation Administration.

Meanwhile, consultants for the Dallas-Fort Worth airport concluded that the Dec. 31 deadline would result in three-hour waits at peak times, a scenario that moved its officials to lead an effort to lobby Congress for a delay.

The House passed legislation to delay the luggage screening deadline for as long as a year, but the bill has not come up for a vote in the Senate. A TSA official said that as many as 40 airports would not make the deadline, but would not say which ones, citing security concerns.

The Los Angeles airport will get 49 minivan-sized CTX machines, which use CAT-scan technology to check for explosives. It will also get 251 "trace detection" machines, which require a screener to rub a piece of gauze on the bag or inside it, and then test the swab for explosive residue. Some trace machines will be affixed to airline ticket counters and others will be on mobile carts that will plug into terminal floors.

Kim Day, Los Angeles airport's deputy executive director of project and facilities development, said the airport began planning in February. The attitude was to "not just let these people who don't know our airport come in here and do stuff," Day said.

By the time the TSA sent its first contractors to evaluate the Los Angeles airport, local officials had already visited several airports where bomb-scanning machines were being tested and were able to present the TSA with a lot of critical information. Despite the preparations, it took weeks to work out details.

The TSA's consultants first "came back with a solution that filled the lobby with CTX machines and we would have had 80 percent of passengers out the door," said Frank Clark, who represents 30 international airlines

In September, TSA officials proposed a plan, also opposed by the airport and the airlines, that became known as "drop and go." The idea was that passengers would check in at the airline ticket counters and then drop their bags at a station of luggage-screening machines in the lobby, where a screener would use one of several machines to scan them for explosives. The passenger would then continue on to the security checkpoint and go to their flight.

In meetings, the airlines and airport officials pointed out that the plan would create logistical problems, because it was not clear who would be responsible for making sure that the bags, once screened, got on the right plane. To the airlines, it sounded like an operational nightmare.

Stone said the TSA revised its plans in response to airport and airline concerns. "We didn't sit there and say no, we're going to do it our way," he said.

"To their credit, they listened," Clark said.

Other airports have argued that installing the machines now could cause huge delays during the holiday travel period. But Day said the airport expects 90 percent of its travelers to wait only 10 additional minutes to have their bags screened, unless there are last-minute changes in flight schedules.

She acknowledged, however, there could be initial glitches. "It's one thing to look at drawings, it's another matter to see it yourself and go through it as a passenger," Day said.

A worker at Los Angeles International Airport used a bomb-detecting scanner on luggage in January. Airports face a Dec. 31 deadline for screening all bags.