Were you looking for the variant introduced in Halo: Combat Evolved, the Type-26 Banshee, or the space fighter variant, the Type-27 Banshee?
The Type-54 Ground Support Aircraft (T-54 GSA), also known as the Hesduros-pattern Banshee, more commonly known as the Banshee by UNSC forces, is a standard ground assault aircraft in service with various Covenant remnant factions. 
The Type-54 Ground Support Aircraft is the Hesduros-pattern variant of the Banshee combat flyer. Not restrained by the conservative San'Shyuum bureaucrats of the Covenant, the model features a design that harkens back to earlier Banshee models once used by the Sangheili on their homeworld, Sanghelios. The new model features numerous improvements, including energy shielding. Like the T-26B, the T-54 can be modified to operate in space.
The Type-54 GSA was put into service after the end of the Human-Covenant War, with the Covenant remnants utilizing new manufacturing facilities to manufacture the model. The Type-54 was used in multiple battles, including the Battle of Kamchatka and various battles in the Blooding Years. Around the same time T-54 Banshees became popular in War Games matches aboard the UNSC Infinity.
During Operation: BIRD IN HAND in October 2558, Blue Team hijacked several Covenant Banshees to destroy Argent Moon's reactor cooling system, allowing them to scuttle the station. With the Banshees being too slow to escape the explosion in time and their Pelican presumably destroyed, Blue Team abandoned the craft in favor of the Winter-class prowler ONI Acrisius.
Changes from the Type-26 Banshee in Halo 2 Anniversary
List of appearances