We present an ultrawideband frequency-modulated continuous-wave radar for airborne measurements of snow thickness. The radar operates over a frequency range of 2-18 GHz and is capable of about 1.4-cm range resolution at a nominal survey altitude of 500 m. The system was installed on a Twin Otter and used to collect data to demonstrate the capability of fine-resolution measurements of snow thickness over both sea ice and land near Barrow, AK. Data collected over a relatively smooth water surface, a lead, were used to deconvolve system effects to reduce range sidelobes and obtain close-to-ideal range resolution. Radar data collected over snow covered sea ice and land from the field campaign showed that we can map air-snow and snow-ice interfaces of thin and thick snow. The radar-derived snow thickness data are in a very good agreement with the in situ measured data with a correlation of 0.88.