  In the paper we investigate integrability characteristics for the
dispersionless Kadomtsev-Petviashvili hierarchy. These characteristics include
symmetries, Hamiltonian structures and conserved quantities. We give a Lax
triad to construct a master symmetry and a hierarchy of non-isospectral
dispersionless Kadomtsev-Petviashvili flows. These non-isospectral flows,
together with the known isospectral dispersionless Kadomtsev-Petviashvili
flows, form a Lie algebra, which is used to derive two sets of symmetries for
the isospectral dispersionless Kadomtsev-Petviashvili hierarchy. By means of
the master symmetry, symmetries, Noether operator and conserved covariants,
Hamiltonian structures are constructed for both isospectral and non-isospectral
dispersionless Kadomtsev-Petviashvili hierarchies. Finally, two sets of
conserved quantities and their Lie algebra are derived for the isospectral
dispersionless Kadomtsev-Petviashvili hierarchy.
