1. In and over those parts of the contact zone which are physically controlled by friendly forces and in and over those areas the physical control of which is not clearly established, protection for medical aircraft can be fully effective only by prior agreement between the competent military authorities of the Parties to the conflict, as provided for in Article 29. Although, in the absence of such an agreement, medical aircraft operate at their own risk, they shall nevertheless be respected after they have been recognized as such.

2. "Contact zone" means any area on land where the forward elements of opposing forces are in contact with each other, especially where they are exposed to direct fire from the ground.