I'll refer to earlier remarks. NORAD modernization is pursued under the tri-command framework, and that is to signify, as the words in the policy say—“defence against all perils or threats”—that we are concerned with multi-domain approaches to North America. The main concern in the 1950s was with the air domain only; this is how we started. We have evolved at various times throughout our history, and now we are conducting prudent planning and analysis, internal to our headquarters, to take a look at other domains.
The maritime domain is becoming a concern because of the advances in sea-borne cruise missiles and subsurface-related capabilities. Cyber doesn't care about borders or oceans.