Sea ice thickness on basin-scale is an important variable in the polar climate system, however datasets are sparse. The only remote sensing technique capable of obtaining sea ice thickness on that scale are satellite altimeter missions, such as the ICESat and CryoSat-2. The CryoSat-2 satellite was launched in 2010 and is equipped with the Ku-Band radar altimeter SIRAL. CryoSat-2 is part of the ESA’s Living Planet Programme and was especially developed for the observation of changes in the cryosphere. This includes especially the determination of variations in sea ice thickness in the Arctic Ocean. For that purpose it is essential to validate the Cryosat-2 products. The CryoSat Validation Experiment (CryoVEx) combines field and airborne measurements in the Arctic and Antarctica in order to validate CryoSat measurements. Here we report the results from the first combined aircraft and satellite data acquisition over sea ice in the Arctic Ocean. The aircraft was equipped with ASIRAS, an airborne radar altimeter, which was built to simulate the SIRAL sensor on CryoSat-2. During the CryoVEx 2011 campaign in the Lincoln Sea several Cryosat-2 underpasses were accomplished with two aircraft. One aircraft was equipped with ASIRAS and an airborne laser scanner; the second aircraft carried an electromagnetic induction device for direct sea ice thickness retrieval and an airborne laser scanner as well. Both aircraft flew in close formation at the same time of a CryoSat-2 overpass. This is a presentation about the results from comparing sea ice freeboard distribution of laser and radar altimeter measurements with the CryoSat-2 product within the multi-year sea ice region of the Lincoln Sea in spring, with respect to the penetration of the Ku-Band signal into the snow and the effect of surface roughness on the radar range retrieval.