Abstract:We prove an invariance principle for a class of tilted 1+1-dimensional SOS models or, equivalently, for a class of tilted random walk bridges in Z + . The limiting objects are stationary reversible ergodic diffusions with drifts given by the logarithmic derivatives of the ground states of associated singular SturmLiouville operators. In the case of a linear area tilt, we recover the Ferrari-Spohn diffusion with log-Airy drift, which was derived in [12] in the context of Brownian motions conditioned to stay above circular and parabolic barriers.