Air layering is commonly used to propagate Nepenthes which are difficult to root in the
conventional way. The advantage conferred is that the cutting which one wishes to root
is still attached to a root network (i.e., the "mother" plant). Therefore, it can still receive
water and nutirents while it grows roots of its own, at the site of the cut.

This technique has been successfully used with species which are notorious for
their reluctance to root as individual cuttings; e.g., N. burbidgeae.