- This article is about an in-universe event. For the in-game mission, see First Contact.
Two Osean Air Defense Force squadrons, Cyclops and Strider, were conducting reconnaissance over the Stonehenge ruins. For unknown reasons, they were forced to abandon their previous route back to base and directed to take a new route, one that led right through Yinshi Valley, which was home to Erusean radar and anti-aircraft sites.
In order to rescue them, the OADF deployed Spare Squadron—likely due to the unfavorable flying conditions in the valley. During the battle, Spare Squadron successfully destroyed the radar and anti-air sites, but not before being detected. The Eruseans deployed MQ-99s, but Spare squadron shot them down, allowing their allies to withdraw from the airspace.