  A partial wave analysis of antiproton-proton annihilation data in flight at
900 $MeV/c$ into $\pi^0 \pi^0 \eta$ , $\pi^0 \eta \eta$ and $K^+ K^- \pi^0$ is
presented. The data were taken at LEAR by the Crystal Barrel experiment in
1996. The three channels have been coupled together with $\pi\pi$-scattering
isospin I=0 S- and D-wave as well as I=1 P-wave data utilizing the K-matrix
approach. Analyticity is treated using Chew-Mandelstam functions. In the fit
all ingredients of the K-matrix, including resonance masses and widths, were
treated as free parameters. In spite of the large number of parameters, the fit
results are in the ballpark of the values published by the Particle Data Group.
In the channel $\pi^0 \pi^0 \eta$ a significant contribution of the spin exotic
$I^G=1^-$ $J^{PC}=1^{-+}$ $\pi_1$-wave with a coupling to $\pi^0 \eta$ is
observed. Furthermore the contributions of $\phi(1020) \pi^0$ and $K^*(892)^\pm
K^\mp$ in the channel $K^+ K^- \pi^0$ have been studied in detail. The
differential production cross section for the two reactions and the
spin-density-matrix elements for the $\phi(1020)$ and $K^*(892)^\pm$ have been
extracted. No spin-alignment is observed for both vector mesons. The spin
density matrix elements have been also determined for the spin exotic wave.
