In all these molecules ${\mathrm{O}}_2 \mathrm{and} \mathrm{NO}$, is stabilized by removal of electrons because it is having electrons in the anti-bonding orbital. And thus removal of electron from the anti bonding orbital, increases the bond order of ${\mathrm{O}}_2 \mathrm{and} \mathrm{NO}$​. And thus is becomes more stable after removal of electrons. Bond order of ${\mathrm{O}}_2^{+}$is $2.5$ and it is more than that of ${\mathrm{O}}_2$​ which is having bond order as $2$. Similarly Bond order of $\mathrm{NO} \mathrm{is} 2.5 \mathrm{and} \mathrm{that} \mathrm{of} {\mathrm{NO}}^{+} \mathrm{is} 3$.