Phoenix

"A fully autonomous vehicle, the Phoenix is capable of delivering staggering ordnance to a specified target. Hold the Target Painter beam on an object or ground point until it signals target lock. An immediate airstrike follows with the Phoenix releasing its payload directly, if indiscriminately. Held aloft by four pulse ramdrive engines, and plated in Duranium armour, the heavily armoured Phoenix is ponderous, but effective in combat. The Phoenix makes its presence felt on the battlefield briefly, although a vigilant Raptor or Stationary Turret gunner has been known to take them down."

- UT2004 Manual

The Phoenix was originally planned to be a drivable bomber air vehicle, but was cut from the game in that form and instead is summoned by use of the Target Painter to perform an air strike. The Phoenix travels in a straight line towards its target, and begins releasing bombs as it nears the target. These bombs explode in sequence like small Redeemers, killing anyone and anything in a wide area. When a player successfully paints a target for an air strike, all players are warned of an incoming airstrike.

The Phoenix can be shot down to prevent it from completing its bombing sweep. The Shock Rifle works pretty well for this purpose. When destroyed, the bomber will crash down, detonating in a full-size Redeemer explosion on impact.

Trivia
The drivable version of the bomber is still in the game. It can be accessed through the console command "summon OnslaughtFull.ONSBomber", but it can neither turn nor break nor change altitude. That bomber is called the "Dragonfly". To enter it you may need to issue the console command "set ONSBomber EntryRadius 300"