In addition to the human factor, the propulsion system is being analysed directed to reducing vulnerability. Advanced tests and innovative models are being developed to enhance understanding of the tolerance of aircraft engines to particle ingestion, particularly volcanic ash. The eruption of Eyjafjallajökull volcano in Iceland in 2010 reinforced the need for research on the impact of particles on aircraft propulsion systems. This relatively small eruption caused enormous disruption to air travel in Europe, with some 20 countries closing their airspace and affecting more than 100,000 travellers. Research covers aspects such as effective anti-clogging measures, abrasion, and flameout with the objective of making recommendations on acceptable ingestion thresholds, particularly for volcanic ash (EC, 2012).