Platanthera unknown?

On a recent trip to southeastern North Carolina, we saw many orchids and other wildflowers. A group of us met in the Green Swamp Preserve -- a rich, diverse, wild area managed by The Nature Conservancy.

OK... None of us were sure just what species of orchid this is. At first glance, it appears to be Platanthera cristata, but its size and other features lead us to believe otherwise. Is it a hybrid or another species??? This particular plant was 30 inches tall!