The E-221 Warden was an six-engine, mid-range, atmospheric and exoatmospheric-capable early warning and control craft, used by the United Nations Space Command during the Swarm War. Introduced in 2574, the E-221 was based on the spaceframe of the versatile B-221 Scythe, and was used to provide surveillance, command, control, communications and other electronic support functions to UNSC forces. As a result of its heavily swept delta wing shape, powerful engines and abundance of control surfaces and systems, the Warden was able to support a large array of electrical equipment and fuel in its internal capacity, converted from the bomber's massive ordnance bays; this while maintaining extreme speed and agility for a craft of its size.