This Airborne Early Warning and Control variant of the P-3 was nicknamed Sentinel. Eight P-3Bs were converted into AEW&C aircraft, but although the Orion is globally succesful, this variant was never exported. The P-3 AEWs are used by US Customs and Border Protection's Air and Marine Operations for drug interdiction and homeland security missions. This N91LC (BuNo 155299) became N145CS with the CBP.