China’s three biggest airlines are demanding compensation from Boeing over its grounded 737 Max fleet.
Air China, China Southern and China Eastern have filed claims for payouts, according to state media reports.
China’s regulator was the first to ground the fleet in the wake of two deadly crashes involving the US-made aircraft.
It comes on the eve of a meeting of global aviation regulators that will provide an update on the troubled jets.
The Chinese airlines are seeking compensation for losses incurred by the grounded fleet, as well as delayed deliveries of the 737 Max jets, according to reports.
China operates the largest fleet of Boeing 737 Max aircraft and was the first country to take the jets out of service after the Ethiopian Airlines 737 Max 8 crash in March.
The disaster killed all 157 people on board. In October, 189 people were killed in a Lion Air crash involving the same model.
Both crashes were linked to the jet’s Manoeuvring Characteristics Augmentation System, a new feature on 737 Max planes, which was designed to improve the handling of the jet and to stop it pitching up at too high an angle.
Last week, Boeing said it had completed development of a software update for its 737 Max planes.
The planemaker’s entire global fleet of 737 Max aircraft has been grounded since March and the firm is anxious to prove it is safe to return to the skies.
The move by China’s top airlines to seek compensation comes ahead of a closely watched summit of aviation regulators in Texas on Thursday.
The US Federal Aviation Administration (FAA) is due to provide an update on reviews of Boeing’s software fix and new pilot training.
The meeting in Texas will involve 57 agencies from 33 countries, including China, France, Germany and the UK, as well as the European Union Aviation Safety Agency.
But it is unclear if the planes will be back in the air before the end of the critical summer travel season.