The flight attendants would have begun their cabin service.
( ( The ( flight attendants ) ) ( ( would ( have ( begun ( their ( cabin service ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN flight) (NNS attendants)) (VP (MD would) (VP (VB have) (VP (VBN begun) (NP (PRP$ their) (NN cabin) (NN service))))) (. .)))
The flight attendants' cabin service would have begun.
( ( ( The ( flight ( attendants ' ) ) ) ( cabin service ) ) ( ( would ( have begun ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN flight) (NNS attendants) (POS ')) (NN cabin) (NN service)) (VP (MD would) (VP (VB have) (VP (VBN begun)))) (. .)))