Methods, systems, and devices for wireless communications are described. A relay node may receive, from a source node, control signaling configuring the relay node to receive a transport block via a first air interface and to forward the transport block to a target node via a second air interface that is different than the first air interface. In some cases, each of the first air interface and the second air interface may support a same size transport block. The relay node may receive, from the source node via the first air interface, a first message including the transport block in a format of the first air interface based on the control signaling. The relay node may transmit, via the second air interface to the target node, a second message including the transport block and an indication that the transport block is in the format of the first air interface.