Canonical model for IFT. Step 1: IFT-A and IFT-B complexes, kinesin-2, and inactive cDynein1b gather at the base of the flagellum. Step 2: the active kinesin-2 transport IFT-A and IFT-B complexes, inactive cytoplasmic dynein 2, and axonemal precursors from the base to the tip. Step 3: kinesin-2 reaches the distal end, where axonemal cargo proteins and IFT particles are released into the ciliary tip compartment. IFT-A and IFT-B complexes dissociate from each other. Complex A binds to active cytoplasmic dynein 2. Step 4: active cytoplasmic dynein 2 transports complexes IFT-A and IFT-B and kinesin to the cell body. IFT, intraflagellar transport.