In combating the threat of irreversible climate change, all sectors will need to reduce their carbon dioxide emissions and wider environmental impact. In addition, the rising cost of fuel and maintenance and the quest for continual improvement in aircraft performance has led the aviation industry to the challenge of transitioning from traditional mechanical systems and subsystems to electrical equivalents. In this work, different electrode configurations, simulating the divergent field distributions present in aircraft electrical systems, are examined with adjustable gap distance and variable pressure to simulate flying altitudes. The temperature and humidity in the test vessel are monitored continuously during the tests, but not controlled. We present initial results showing the effect of atmospheric pressure on the partial discharge inception and breakdown voltages in standard electrode configurations.