The finding also calls into question the effectiveness of the Security Security Administration's clandestine program of placing plainclothes agents on commercial flights to detect and respond to in-flight threats.
The Inspector General said that he "had identified $ 394 million of funds that could be used more effectively."
The ministry's most recent budget documents indicate that the budget for the Federal Air Marshal Service, or FAMS, is about $ 803 million.
"The TSA appreciates the work of the Inspector General's Office," said the agency in a statement. "The Federal Air Marshal Service continues to develop its mission tactics in the face of threats to transportation safety.While we can not comment on the details of the OIG recommendation because of its sensitive nature, the TSA continues to Examine and explore methods and capabilities to further reduce all risks to aviation safety. "
The Inspector General's note did not specify whether the TSA agreed or disagreed with its recommendations. The Office of the Inspector General did not immediately return a request for comment.
With the exception of the summary released Tuesday, the report remains classified.
TSA Administrator David Pekoske has already defended the Air Marshal program, saying it reduces risks to aviation.
"I really think the Air Marshals provide a significant layer of security," he told reporters during a conference call last May. He added that it is difficult "to measure the success of prevention".
The summary did not reveal whether the two reports describe the same waste. It also did not explain the vulnerabilities uncovered during the more recent review, nor did it explain how the funds were spent, describing the details as categorized.