According to the US Geological Survey, there are at least 50 years of known helium reserves based on current consumption. 600 Airlander aircraft would account for just 1% of annual helium consumption. Aviation equipment is normally scheduled to be in operation in excess of 25 years. Once the Airlander is filled it does not consume helium, it stays filled with the same helium as from its inception, less a tiny annual leakage.