Your country does not have defensive radar planes. Radar planes are important for your defence. If you are attacked, your air force will be more effective in defending your country if it gets information on where the attack will hit. This information is only available if you have radar planes. Make sure you have at least three and defend your defensive air force base heavily to prevent their destruction. Your enemy will try to destroy these radar planes because attacks on targets in your country become easier when the radar planes are out of action.