During the Battle of Earth, the Pony Express was at Earth fighting the Covenant. After receiving a message from Dr. Halsey, Lord Hood planned on sending the Spartan-IIs to Onyx aboard the Pony Express, but they opted to instead capture a Covenant destroyer, the Bloodied Spirit, which was faster than even the Pony Express.
- The Pony Express is a reference to the old mail system where riders would take fast horses from checkpoint to checkpoint, picking up mail and getting a new horse at each one. It lasted from April 1860 to October 1861, only slightly more than a year, but it made a major impact.
- Halo: Ghosts of Onyx (First appearance)