The sometimes rocky relationship between Perth Airport and its largest customer Qantas, critical to the Western Australian economy, has sunk to a new low with the issuing of a writ for $A11.3 million in the WA Supreme Court today to recover unpaid charges for aeronautical services used by the flying kangaroo. In a statement, Perth Airport said that for “more than 18 months it has been offering a new Aeronautical Services Agreement to Qantas which would have delivered the airline a significant price reduction compared to charges paid by Qantas pursuant to the previous agreement which expired on 30 June 2018.” “All other airlines which use Perth Airport had reached an agreement with Perth Airport on charges for aeronautical services, effective 1 July 2018,” the airport said. Qantas, however, had not but as an act of good faith Perth Airport said it “began invoicing Qantas at the proposed reduced rate from 1 July 2018.” “Despite the reduced price offered, Qantas unilaterally decided to short pay these invoices by around 40 percent,” the airport alleges. “The amount now outstanding (July-October) totals approximately $11.3 million which constitutes a material amount of revenue and is not sustainable,” the airport said. Read: The world's best airlines 2019 Perth Airport said that it had made numerous attempts to negotiate an outcome with Qantas, but these have failed to resolve the issue. “Accordingly, to bring the issue to a head as soon as possible Perth Airport was forced to commence legal action against Qantas in the WA Supreme Court.” Perth Airport assured the public that the legal action will not impact Qantas's operations at the airport. However, it warned that “failure to resolve the short payment of aeronautical charges by Qantas could have potential implications for Perth Airport’s ability to provide services and build additional capacity in the future to meet the needs of its airline partners and the traveling public.” At risk is the much-touted Perth to Paris non-stop flight, the expansion of the airport and building of a third runway. Qantas is also in a similar tussle with Darwin and Alice Springs airport, with the latter considering legal action. But Qantas Domestic chief executive Andrew David said yesterday that the airline is “willing to pay fair and reasonable charges but want to ensure that our customers are not paying more in airport charges than is absolutely necessary.” “Perth Airport is one of the most expensive domestic airports that we fly to in Australia,” said Mr David. He added that “without agreement or reasonable justification, Perth Airport has been sending us invoices for higher fees and charges, when these were already too high, to begin with.”