By John Crawley WASHINGTON, April 24 (Reuters) - The Bush administration restructured a key element of airport security on Wednesday, dramatically reducing plans to buy large $1 million machines to scan checked luggage for bombs. For the first time, Transportation Department officials provided concrete figures for the type and number of devices it will need to screen bags at more than 420 U.S. airports by the end of the year. The government now plans to deploy up to 1,100 large explosive detection machines, also known as EDS, that scan bags for bombs and 4,700 so-called trace machines that zero-in on explosive residue. Trace devices cost about $40,000 each and require screeners to operate. The larger EDS equipment use computer technology to scan luggage on a conveyor and require visual confirmation of a weapon or bomb. Until now, government estimates called for installation of more than 2,000 EDS devices that retail at roughly $1 million to make and $1 million to install. The government is getting a price break from manufacturers for bulk orders, but officials did not reveal the discount. Fewer than 200 EDS machines are already in place at several airports, and the government recently placed firm orders for 400 more from two manufacturers, L-3 Communications (LLL) and InVision Technologies Inc. (INVN). Plans call for other companies to make them as well to speed production and meet a congressional mandate that bomb detection equipment be in place at airports by the end of December. Faced with the daunting challenge of installing EDS machines -- which rival a sport utility vehicle in size - under tight time constraints, transportation officials acknowledged several weeks ago they would likely use a mix of bag screening technologies. But the Bush administration, until now, had not settled on an approach or given any firm idea of what bag screening would cost. Congress demanded that the Transportation Department firm up numbers for explosive detection requirements before it would fund more money to buy them. The new Transportation Security Administration has requested $4.4 billion in funding this year to pay for explosive detection technology and overhaul passenger screening operations with a federal work force. Separately, Transportation Secretary Norman Mineta announced the government had awarded Lockheed Martin Corp. (LMT) a $105 million contract to train airport screeners. The Transportation Security Administration plans to employ roughly 30,000 screeners by the end of the year. Hundreds of them have already been hired. The first screeners will debut at Baltimore-Washington International Airport at the end of the month, transportation officials said. ©2002 Reuters Limited.