From Halopedia, the Halo wiki
The Covenant bomber was a Covenant unit cut from Halo: Combat Evolved. It was presumably meant as a heavy aerial weapons platform, a supplement to the smaller, lighter Banshee, but was cut from the released game. It featured two forward-swept wings, akin to the twin booms of the Spirit dropship, and had a long protrusion underneath, which may have been an underslung weapons mount or landing gear.
The bomber was first revealed by Paul Russel on his twitter account with a number of other concepts that were ultimately cut from the final game.