The agency created to oversee airport security after the Sept. 11 attacks is losing its third director in as many years, after the White House requested his resignation, officials said on Friday. David Stone will step down within months as head of the Transportation Security Administration, a target of congressional and other critics who question its relevance and recoil at its spending. The TSA's proposed budget for fiscal 2006 is $5.6 billion. Brian Roehrkasse, Homeland Security Department spokesman, said Stone announced his intention to leave but has been asked to stay for a few months. Shortly after he took office in February, Homeland Security Secretary Michael Chertoff ordered a complete review of homeland security functions to see what type of restructuring may be necessary. "TSA, like all of the department's components, is included in the review," Roehrkasse said. Stone is a former Navy rear admiral who oversaw TSA security at Los Angeles International Airport before being named the agency's acting administrator in December 2003. He was confirmed by the Senate last July. --More 2244 Local Time 1944 GMT