...American Airlines policy prevents anyone from accumulating a 4.75% stake or more without board approval, and the company’s board said it hasn’t received a request from Qatar Airways to go above that threshold. Further, foreign ownership laws limit the total percentage of foreign voting interest to 24.9%, American said.

As of March and April filings, the company had five shareholders above the 4.75% threshold including Warren Buffett’s Berkshire Hathaway Inc. which has a 10% stake....