The first successful flight of Zveno-1, using a Tupolev TB-1 mothership and two Tupolev I-4 fighters mounted on top of the wings, took place on 3 December 1931. An error in the sequence of opening the latches by the bomber crew resulted in one of the fighters prematurely separating, but the TB-1 with an I-4 attached to one of the wings remained in controlled flight and the second fighter was soon uneventfully deployed. After latch control was fully moved into the fighters, the normal launch procedure consisted of pilots opening the tail lock and then pulling on the control stick to open the front locks and separate from the bomber. As predicted, the presence of docked fighters had a minimal impact on performance of the mothership, and Zveno-2 Tupolev TB-3 carrying three Polikarpov I-5 fighters handled the same as an ordinary bomber. To mount the aircraft on the wings, they were pushed up special ramps but the centerline aircraft had to be lifted on top of the fuselage by hand. This was so cumbersome that the centerline I-5 became a permanent fixture on top of the Zveno-2 TB-3 and never started in the air. At one point, the centerline I-5, still with a pilot at the controls to operate the engine, had the wings and the tail surfaces removed and was used purely as fifth powerplant for the bomber mothership.