As The New York Times exposes, within the $600 billion annual Defense Department budgets, the $22 million spent on the program was almost impossible to find.

Which was how the Pentagon wanted it.

For years, the program investigated reports of unidentified flying objects, according to Defense Department officials, interviews with program participants and records obtained by The New York Times. It was run by a military intelligence official, Luis Elizondo, on the fifth floor of the Pentagon's C Ring, deep within the building's maze.

The Defense Department has never before acknowledged the existence of the program, which it says it shut down in 2012. But its backers say that, while the Pentagon ended funding for the effort at that time, the program remains in existence. For the past five years, they say, officials with the program have continued to investigate episodes brought to them by service members, while also carrying out their other Defense Department duties.