Attempts were made during two field experiments to fly instrumented aircraft along absolute momentum (M) surfaces as a means of accurately determining slantwise convective stability. The application of this technique appears to have been quite successful. We present the results of four such efforts conducted in the ascent regions of midlatitude cyclones observed during the New England Winter Storms and Genesis of Atlantic Lows Experiments. In three of the four cases the atmosphere was almost exactly neutral to slantwise ascent while being quite stable to vertical displacements. In the fourth case, the atmosphere departed from neutrality but was also substantially drier, evidently due to subsidence. We find excellent agreement between assessments of stability based on the M surface flights and on cross sections constructed from rawinsonde observations. On the basis of these results I hypothesize that slantwise convective neutrality is characteristic of the ascent regions of baroclinic cyclones and discuss the implications of this finding for the dynamics of baroclinic systems.