In situ electron density measurements from the CHAMP satellite and global positioning system total electron content (TEC) observations are used to illustrate how quasi-16-day planetary wave activity influences the structure of the low-latitude ionosphere. SABER temperature measurements reveal that quasi-16-day oscillations in the dynamo region (110 km) during the time interval of 1 December 2005 to 1 March 2006 are most dominant in the zonal mean. Enhancements in equatorial zonal mean temperatures in the E-region are connected with enhancements at ±10–20° magnetic latitude in zonal mean CHAMP electron densities and TEC. At a near-constant altitude of 350 km, the oscillations in daytime electron densities are greater than 40 percent of background levels. A local time effect is also observed in the planetary wave influence on the F-region electron densities. These results demonstrate that vertically propagating planetary waves induce significant variability in the low-latitude F-region ionosphere and that these effects are seen at all longitudes.