Reactive nitrogen compounds play an essential role in the processes that control the ozone abundance in the lower atmosphere, in particular HNO3, which is one of the principal reservoir species for the nitrogen oxides. However, there remains a significant lack of data for simultaneous observations of O3 and HNO3, despite the fact that the correlations between these species are particularly important for characterizing air masses and evaluating how ozone depends on nitrogen compounds. As a consequence, the chemical link between O3 and HNO3 remains poorly known in the lower layers. In this study, we use aircraft observations of O3 and HNO3 from the NASA ARCTAS and NOAA ARCPAC campaigns during spring and summer of 2008 together with O3 and NO2 satellite data respectively from the IASI and the OMI instruments and a global chemical transport model (MOZART-4) to better understand the sources, transport and variability of these compounds in the Arctic. FTIR measurements of O3 and HNO3 made at Eureka and Thule during the ARCTAS mission are also used for our analysis. The results are discussed in terms of O3-NOy chemistry and the role of HNO3 as a reservoir of NOx is investigated. These analyses also help us to quantify the contribution of the stratosphere to the tropospheric ozone budget in the Arctic.