It is well known that NO+ ions constitute about 45% of the product ions of the ionospherically important reaction of N+ ions with O2. However, NO+ ions in both the ground X 1Σ+ state and the metastable a 3Σ + state are energetically possible. The present study uses a selected-ion flow tube to determine the percentage of NO+(a 3Σ+) product ions. It is known from separate studies that NO+(a 3Σ+) ions react rapidly with N2 to form N2+; therefore, the addition of N2 and the occurrence of N2+ ions provide a monitor for the possible NO+(a 3Σ+) product ions from the N+ reaction with O2. It is found that NO+(a 3Σ+) production accounts for less than 2% of the total rate constant at 300 K.