O que é “Área de defesa” em um gráfico secional VFR?

O que é "Área de defesa" em um gráfico seccional de VFR? As palavras "ÁREA DE DEFESA" (em letras maiúsculas) aparecem ao longo da fronteira EUA / México em azul. É o maior texto no gráfico. Curiosamente, as mesmas palavras não parecem estar ao longo da fronteira dos EUA / Canadá.

Alguém em airliners.net disse isso:

You're correct, there is a difference between a ADIZ and a Defense Area. A defense area is an area established on non-federal lands located within the United States, its possessions or territories, for the purpose of safeguarding classified defense information or protecting government equipment and/or material.

The establishment of a national defense area temporarily places such non-federal lands under the effective control of the Department of Defense and results only from an emergency event.

I am surprised that it is charted though, unless of course the government is getting ready for the flood of illegals coming to California to get drivers licenses and registering to vote.

Isso faz com que pareça uma coisa do chão, não uma coisa do ar. Então há isto, no CFR 99.3:

Unless designated as an ADIZ, a Defense Area is any airspace of the United States in which the control of aircraft is required for reasons of national security.

E no CFR 99.49:

All airspace of the United States is designated as Defense Area except that airspace already designated as Air Defense Identification Zone.

E no objetivo:

Defense Area means any airspace of the contiguous U.S. that is not an ADIZ in which the control of aircraft is required for reasons of national security.

Então, o que é exatamente essa Área de Defesa no meu Diagrama de Seção e eu preciso me preocupar com isso ou pensar nisso enquanto voo?

A partir da citação do CFR 99.3, o que isso significa?

in which the control of aircraft is required for reasons of national security