Hainan Airlines (HU, Haikou) suspended the trading of its shares on the Shanghai Stock Exchange on January 10 as a precursor to a major restructuring, potentially to relieve the debt burden of its parent HNA Group.

On January 12, Tianjin Tianhai Investment Co., another HNA Group subsidiary, also suspended trading.

Both the airline and the shipping company said in their respective regulatory filings that the suspension is pending a major announcement regarding assets restructuring.

HNA Group said on January 9 it had pledged its listed subsidiary's shares to the Industrial and Commercial Bank of China as collateral to cover its cash needs. Neither of the companies announced the details of the restructuring nor announced when will they resume trading.

The South China Morning Post said the Hainan-based conglomerate took on significant debt in last years due to its shopping spree which saw it acquire dozens of companies around the world, including Avolon, Gategroup, Servair, SR Technics, CIT Aerospace along multiple other travel, property, logistics and financial firms. It either owns or holds stakes in Azul Linhas Aéreas Brasileiras, TAP Portugal, Comair (South Africa), Virgin Australia, Frankfurt Hahn and Rio de Janeiro Int'l airports, Hilton Worldwide Holdings, Swiss travel retailer Dufry, and Deutsche Bank, as well as many Chinese carriers, among others.

HNA Group's ownership structure is notoriously complicated and obscure. Bloomberg recently reported that in total there may be as many as 518 companies related by ownership to Hainan Airlines.