WASHINGTON — Managers at some major airports believe big travel problems could lie ahead come the Dec. 31 deadline to begin inspecting every piece of checked luggage for explosives. They also are raising questions about whether the bomb-screening equipment is sophisticated enough and in adequate supply.

        The prospect of long lines and finding space for the minivan-sized machines in already cramped airports have led Congress to consider delaying the screening requirement by a year.

        “I see disaster coming,” said Bruce Baumgartner, aviation manager at Denver International Airport. “If it doesn't work and people are inconvenienced, people are going to stop flying.”

        Airports without enough of the explosive detection machines in place by year's end must check bags with smaller hand-held equipment that finds traces of explosives.

        The trace detectors require more employees and take longer to examine luggage than the larger machines.

        Without enough employees and equipment, passengers could face waits of three hours to have their baggage checked for explosives, said Kevin Cox, senior executive vice president at Dallas/Fort Worth Airport.

        “It will be catastrophic,” he said.

        Congress, which imposed the deadline in security legislation passed after Sept. 11, is having second thoughts. The House last month voted 217-211 to extend the deadline by a year. A Senate committee will consider the idea when lawmakers return from their summer vacation in September.

        Rep. Peter DeFazio, a member of the House Transportation aviation subcommittee, said Sunday that the deadline should be met to prevent terrorists from blowing up an airplane with explosives hidden in luggage, as was done on Pan Am Flight 103.

        “I believe an explosives attack is much more likely than a takeover,” said DeFazio, D-Ore., on NBC's “Meet the Press.”

        Some airport managers say the government is installing obsolete equipment. They say the two systems licensed for use at U.S. airports are slow and often mistake ordinary substances for explosives.

        Jerry Orr, aviation director at North Carolina's Charlotte/Douglas Airport, calls the machines “yesterday's news.”

        “We ought to take whatever time is necessary to do it right the first time,” Orr said.

        Baumgartner said the federal government should wait for better equipment. With the current bomb-detection machines, which detect only density and shape, “you can't tell the difference between chocolate and plastique explosives,” he said.

        Richard Lanza, a Massachusetts Institute of Technology scientist, said the U.S. machines — made by InVision Technologies of Newark, Calif., and L-3 Communications of New York — do not always distinguish between plastic explosives and chocolate. Still, he said, “of all the possible technologies, I think they're the best.”

        The Transportation Security Administration said it plans to meet the year-end deadline by buying 1,100 of the large explosive detection equipment and 4,000 trace machines.

        “We are on pace at this point to meet that deadline,” TSA spokesman Greg Warren said.

        InVision and L-3 said they would deliver 114 machines by the end of June. The Transportation Department's inspector general said 100 were delivered and only 29 of them were working as of July 27.

        David Pillor, InVision's executive vice president, said it takes time to install the machines. “We're pretty close to our delivery schedule,” he said.

        Messages left for a spokesman for L-3 were not immediately returned.

        Pillor said a bomb-detection machine operator can tell within 20 seconds whether a substance is chocolate or plastique by looking at the shape, size or whether it has a detonator. If the machines are slow, he said, it's either because of a poorly trained operator or because they're part of an inefficient bag-handling system.

        At Boston's Logan Airport, officials decided they needed to build 11 baggage-screening rooms, make seven major building additions and install five new electrical substations. It is unclear whether the airport will meet the deadline.

        “It's going to be tight,” said Craig Coy, executive director of Massport, which runs Logan. “I touch wood every day.”

        Hal Wight, who manages the tiny airport in Klamath Falls, Ore., said he will have to move some walls, remodel the ticket counters and change the baggage belt to make room for federal employees to check baggage with hand-held equipment.

        “I don't think everything will be in place on time,” he said.

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