It is shown that explanations of atmospheric neutrino anomaly other than nu
(mu) - nu (tau) oscillations (e.g. decay, decoherence and nu (mu) - nu (ta
u) - nu (KK) mixing) can be tested at future facilities. Stringent tests of
CPT invariance in neutrino oscillations can also be performed. (C) 2001 El
sevier Science B.V. All rights reserved.