WASHINGTON \u2014 The Federal Aviation Administration is bringing thousands of furloughed inspectors and other employees back to work as the partial government shutdown drags on, the agency said Tuesday. The F.A.A.\u2019s announcement came after unions representing aviation safety inspectors and air traffic controllers raised concerns that the lengthy shutdown was eroding the safety of the United States\u2019 air travel system. It is one of the largest changes made by a government agency to address the need to maintain an essential service since the shutdown began last month. The Internal Revenue Service is planning to bring back tens of thousands of furloughed workers for tax season, and the Food and Drug Administration has said it is bringing hundreds of workers back to step up food safety inspections. Under its revised shutdown plan, the F.A.A. will have 3,113 employees in its aviation safety organization who are considered essential to protect life and safety, and those employees will work without pay. Under its original shutdown plan, only 216 aviation safety positions were considered essential for life and safety. Over all, under the revised plan, about 14,000 of the F.A.A.\u2019s 45,000 employees will be furloughed, down from 18,000. \u201cWe are recalling inspectors and engineers to perform duties to ensure continuous operational safety of the entire national airspace,\u201d the agency said Tuesday in a statement. \u201cWe proactively conduct risk assessment, and we have determined that after three weeks, it is appropriate to recall inspectors and engineers.\u201d Mike Perrone, the national president of the Professional Aviation Safety Specialists, which represents aviation safety inspectors, said Tuesday that the inspectors should have been considered essential employees \u201cfrom Day 1.\u201d Getting his members back to work, he noted, does not solve another problem: They still will not receive paychecks. \u201cOur bottom line is still, Priority 1, open the government,\u201d he said. Air traffic controllers are among the employees who have been working without pay throughout the shutdown. T heir union, the National Air Traffic Controllers Association, sued the government last week over it. The union asked a judge to issue a temporary restraining order and instruct the government to provide the controllers with the pay they have missed. But on Tuesday, Judge Richard J. Leon of Federal District Court in Washington denied their request, as well as two others for temporary restraining orders that were made by another union and a group of federal workers. The shutdown has also prevented the National Transportation Safety Board from investigating about a dozen transportation accidents. The board said Tuesday that it would recall several investigators after the discovery of the cockpit voice recorder from the Lion Air plane that crashed into the Java Sea in October after taking off from Jakarta, Indonesia.