Between 1981 and 1985, absolute time of arrival (TOA) measurements were made on HF sky wave time standard signals at different frequencies. A total of 113 path months of TOA data were collected over a one‐hop path between Fort Collins, Colorado and San Diego, California. In addition, 15 path months of data were collected between Fort Collins and Oahu, Hawaii, and 12 path months were gathered on signals between Tokyo, Japan and Oahu. The data show a higher degree of ionospheric movement than had been expected by the experimenters. They also show a higher degree of stratification within layers than can normally be explained with simple models based on a single‐layer ionosphere.