The military won't give access to the decryption keys to that many organizations, especially foreign organizations. The crypto tech and keys are both classified, so anyone handling a unit would have to be given at least Secret clearance. Anyone doing the key updating would need to have Top Secret clearance (I think, not 100% on that). Every plane would have to be constantly monitored at all times (both in flight and while at foreign airports) by cleared personnel to ensure the boxes aren't taken by adversarial states.