Several two-seat trainer variants of the Me 262, the Me 262 B-1a, had been adapted through the "Umrüst-Bausatz 1" factory refit package as night fighters, complete with on-board FuG 218 "Neptun" high-VHF band radar, using "Hirschgeweih" ("stag's antlers") antennae with a set of dipole elements shorter than the "Lichtenstein SN-2" had used, as the B-1a/U1 version. Serving with 10. "Staffel" "Nachtjagdgeschwader" 11, near Berlin, these few aircraft (alongside several single-seat examples) accounted for most of the 13 Mosquitoes lost over Berlin in the first three months of 1945. Intercepts were generally or entirely made using "Wilde Sau" methods, rather than AI radar-controlled interception. As the two-seat trainer was largely unavailable, many pilots made their first jet flight in a single-seater without an instructor.