Operational update
Our Civil Aerospace business has experienced a significant reduction in demand due to the effects of COVID-19. Widebody engine flying hours fell by approximately 50% in the first half, compared to the prior year period with an approximate 75% decline in the second quarter. Since the low point in April, when flying hours were down 80% compared to April 2019, we have seen early signs of recovery with a marginal improvement in May and June led by an increase in flights in China, Asia Pacific and the Middle East. Business jet and regional flight activity has been recovering more quickly due to lower exposure to cross-border routes.
MRO (Maintenance, Repair and Overhaul) activity in the first half was broadly stable compared to the prior year period but lower than the pre-COVID-19 first half schedule. We have completed the backlog of overhauls related to the Trent 1000 durability issues and have achieved our target to reduce the number of related aircraft on the ground (AOG) to single digits. We are progressing well with the type test of the replacement high pressure turbine blade for the Trent 1000 TEN, the final durability issue to be fixed, and remain on track for its incorporation into the fleet by the end of H1 2021.
The deterioration in the medium-term market outlook for the commercial aviation industry will need to be reflected in our contract accounting assumptions and we will also be assessing the carrying value of our engine programmes and deferred tax assets. We are currently undertaking a review of these matters, the impact of which may result in non-cash accounting adjustments in our first half results.
Output of new widebody engines was consistent with our revised guidance of 250 engines for the full year, with 130 engine deliveries in the first half.
The commercial aerospace activities of ITP Aero, which account for approximately 75% of its business, have experienced a similar deterioration in end market demand as our Civil Aerospace business unit. Its defence related activities remained stable.
Our Power Systems business experienced varying levels of COVID-19 related disruption and utilisation with low double-digit percentage revenue decline compared to the prior year period. Our customers in industrial markets were the most impacted by lower activity levels, particularly those with exposure to oil & gas and mining. PowerGen activity also slowed down in the second quarter, most notably in the US. We experienced a reduction in demand for smaller yacht engines with some marine yards closed for much of the second quarter. Defence related activities and the rest of our Marine business performed relatively robustly. Long-term demand growth for reliable power solutions is expected to remain intact with demand in data centre mission critical applications increasing above pre-COVID levels. We are growing market share in developing markets, particularly in China where we continue to expect growth in our revenues in 2020.
Our Defence business has remained resilient with continued demand from key government customers. We have not experienced any material operational or financial disruption as a result of COVID-19. We remain committed to the development of new products and programmes in Defence including Tempest in the UK. In the US, we are poised to submit our RFP for the new B-52 engine opportunity and the consortium of which we are a member recently went through to the next round in the competition for the US Army’s Future Long Range Assault Aircraft.