Qatar wants 10% of American Airlines
American Airlines has received an "unsolicited" approach from Qatar Airways which wants to acquire 10% of the US carrier.
In a regulatory filing, American Airlines said Qatar intended to purchase at least $808m (£638m) of its shares.
American Airlines said it would respond "in due course".
Shares in American Airlines, which is the biggest airline in the world, were up by about 3.5% in early trading.
In 2015, Qatar Airways took a 10% stake in International Airlines Group (IAG), the owner of British Airways and Iberia.
Then in July 2015 it increased its stake to 20%, becoming IAG's biggest shareholder.
Earlier this month, Saudi Arabia, Egypt, Bahrain, the United Arab Emirates, Libya, Yemen and the Maldives cut diplomatic ties with Qatar.
Saudi Arabia, the UAE, Bahrain and Egypt all said they would stop flights in and out of Qatar, and close their airspace to the country's flag carrier, Qatar Airways.