When the Omega Comet passed by the planet of Arus, the team were consumed by it, and sent into the Robotech universe. This event caused an alternate timeline in both universes.
In the Robotech universe, the Lion Force crashed into Breetai's Flagship, killing both Breetai and Exedore in the process. The SDF-1, in an orbit around the Earth at the time, was forced into a Space Fold in order to avoid the same fate. In doing so, the ship was also sent into the Comet's range and disappeared.
The mecha broke into its individual pieces, and crash landed on Earth. Four of the segments of the ship landed near Macross Island, (Robotech/Voltron: 1) while the final Lion, along with Allura, its Pilot, landed in Egypt. (Robotech/Voltron: 5)