Perth International Airport has issued a writ of summons to Qantas (QF, Sydney Kingsford Smith) asking for AUD11.3 million dollars (USD8.1 million) in unpaid charges, The West Australian newspaper has reported.

The Western Australian airport, which Qantas uses for, among others, its non-stop services to London Heathrow, said it had been offering a new agreement to the carrier for eighteen months before July 1, 2018. If accepted, the new agreement would - according to the airport - actually lower the fees paid by the airline.

However, Qantas never accepted the new agreement, contrary to all other airlines operating to and from Perth.

The airport further said that despite the lack of agreement, it decided to unilaterally change the agreement on July 1, 2018, and started invoicing Qantas with new, lower fees.

"Despite the reduced price offered, Qantas unilaterally decided to short pay these invoices by around 40 percent. The amount now outstanding (July-October) totals approximately AUD11.3 million which constitutes a material amount of revenue and is not sustainable," the airport said.

Reportedly, Qantas only paid AUD16.5 million dollars (USD11.8 million) out of the invoiced sum of AUD27.8 million dollars (USD20 million).

Perth further said that if it fails to reach an agreement with Qantas over the overdue fees, it will have to reconsider planned investments, including the third runway, and could refuse services to the airline.

The Australian carrier currently operates 338 weekly departures out of Perth and is the largest operator there with a 34.8% market share by capacity, the ch-aviation capacity module shows.

Qantas and Perth have already been at odds for a few months over the use of terminals. In May, the airline said it would suspend its plans to launch further long-haul routes out of the airport - first to Johannesburg O.R. Tambo - as the airport tried to force Qantas to use the international Terminal 1 rather than the adapted part of the domestic Terminal 4, from where its services to London and Singapore Changi depart.

Qantas is also involved in payment disputes with Darwin and Alice Springs.