  Domino tilings of the two-periodic Aztec diamond feature all of the three
possible types of phases of random tiling models. These phases are determined
by the decay of correlations between dominoes and are generally known as solid,
liquid and gas. The liquid-solid boundary is easy to define microscopically and
is known in many models to be described by the Airy process in the limit of a
large random tiling. The liquid-gas boundary has no obvious microscopic
description. Using the height function we define a random measure in the
two-periodic Aztec diamond designed to detect the long range correlations
visible at the liquid-gas boundary. We prove that this random measure converges
to the extended Airy point process. This indicates that, in a sense, the
liquid-gas boundary should also be described by the Airy process.
