An investigation is described of the behavior of NO+ in the daytime F region, with basic ion concentration measurements from the Atmosphere Explorer C satellite. The data set was acquired along select orbits at low latitudes and exhibits substantial variations in the NO+ concentration, both along and between nearby orbits. An excellent consistency is demonstrated between these observations and current chemical equilibrium theory, in contrast to differences that have been reported for the related N2+ ion. Large variations in the concurrently observed electron temperature permit a relevant comparison between different laboratory determination of the dissociative recombination rate coefficients. Contributions to the NO+ production from several seconardy sources are also evaluated. Results strengthen the basis for the current theoretical ionospheric chemistry of NO+ and establish important constraints on resolution of the difficulties with N2+.