The oxygen permeation flux through La1-ySryFeO3-delta (y = 0.1, 0.2) in a large oxygen partial pressure gradient (air/CO, CO2 mixture) was found to be limited by the carbon monoxide oxidation rate at the low oxygen partial pressure side of the membrane. The oxygen permeation flux through the membrane was almost independent of its thickness (1 versus 2 mm) and strontium dopant concentration. The deposition of a 50 nm thin porous platinum layer at the low oxygen pressure side of the membrane increased the carbon monoxide oxidation rate and in this way the oxygen permeation flux by a factor 1.8 +/- 0.2.