Using the techniques of muon spin rotation and torque magnetometry, we investigate the crossover field Bcr in Bi2.15Sr1.85Ca1Cu2O8+δ at which the vortex lattice becomes disordered along the field direction. It is found that Bcr scales as the projection of the applied field along the perpendicular to the superconducting planes. This has the implication that a field large enough to give a disordered lattice when applied perpendicular to the planes, can give a well-ordered vortex-line lattice for angles of the field to the c axis greater than a critical value.