  We report resistivity and upper critical field B_c2(T) data for disordered
(As deficient) LaO_0.9F_0.1FeAs_1-delta in a wide temperature and high field
range up to 60 T. These samples exhibit a slightly enhanced superconducting
transition at T_c = 28.5 K and a significantly enlarged slope dB_c2/dT = -5.4
T/K near T_c which contrasts with a flattening of B_c2(T) starting near 23 K
above 30 T. The latter evidences Pauli limiting behaviour (PLB) with B_c2(0)
approximately 63 T. We compare our results with B_c2(T)-data from the
literature for clean and disordered samples. Whereas clean samples show almost
no PLB for fields below 60 to 70 T, the hitherto unexplained pronounced
flattening of B_c2(T) for applied fields H II ab observed for several
disordered closely related systems is interpreted also as a manifestation of
PLB. Consequences are discussed in terms of disorder effects within the frames
of (un)conventional superconductivity, respectively.
