Shares of Lilium tanked Thursday after the air taxi firm said in a filing that its two main subsidiaries plan on filing for insolvency in the coming days.

The aerospace startup’s shares plunged more than 63% following the news.

In a U.S. regulatory filing, Lilium — which is listed on the Nasdaq — said it had not been able to raise sufficient additional funds to continue the operations of Lilium GmbH and Lilium eAircraft GmbH, the firm’s two main subsidiaries.

As a result, the heads of these subsidiaries “determined that they are overindebted … and are or will become unable to pay their existing liabilities due … within the next few days,” Lilium said.

This is a breaking news story and will be updated shortly.