AIR FORCE ACADEMY, Colo. — The landmark Cadet Chapel at the Air Force Academy will close Jan. 1 for a major restoration project that could take up to four years.

The project was originally expected to start last summer, but the academy said Monday it was pushed back while the school found a contractor with experience in renovating historic buildings.

The restoration includes replacing the chapel's aluminum skin, removing and cleaning 24,000 stained-glass tiles, stiffening the steel superstructure and adding a water barrier.

The academy says the chapel has leaked since it was built and previous repairs failed.

The school said last year the restoration was expected to cost between $58 million and $68 million.

The chapel, a National Historic Landmark, is a striking, triangular-shaped structure that stands 150 feet tall.