The unique operation of the THAI process – Toe-to-Heel Air Injection, enables very high oil recovery and substantial in-situ upgrading. Both thermal upgrading (non-catalytic) and also catalytic upgrading, in which a catalyst is emplaced along the horizontal producer well, were investigated. 3-D physical model experiments were conducted on virgin Athabasca Tar Sand bitumen to investigate dry and wet combustion performance. These results were compared against those from a steamflood test, which was also followed by air injection. Excellent ignition and very stable combustion propagation was achieved using Athabasca Tar Sand. Thermal upgrading achieved nearly 10 API points increase. Additional upgrading was achieved using an in situ catalyst. The main limitation of using steam is that a very large fraction of the oil remains immobile. This residual oil can only be ‘unlocked’ by thermal cracking at high temperature (>500°C), as in THAI. THAI has the extra advantage that some hydrogen is generated in situ, providing further significant upgrading via hydroconversion. There are also substantial environmental benefits because of the large reductions in sulphur and heavy metals in the produced oil. Furthermore, oil is produced without ‘displacement delay’, immediately ahead of the combustion front. The Oil recovery using THAI was greater than 75% OOIP.