Aircraft data have been traditionally ingested in data assimilation systems as single-level data, since the majority of the aircraft reports occur at cruising altitudes. However, vertical profiles from ACARS-equipped commercial aircraft during ascent or descent can provide high-quality in-situ information about the vertical structure of temperature and momentum in the atmosphere at intervals of 90 m to 600 m. Previous research has shown that these observations are at least as accurate as rawinsonde observations, suggesting that they should be of considerable benefit to data assimilation. Examples from experiments using the Navy's 3DVAR data assimilation system are presented, comparing the use of aircraft "soundings" with rawinsonde soundings. The 3DVAR system is ideally suited to this comparison, since it computes the analysis in observation space at points where profiles are available.