American Airlines Group Inc's top six executives on Tuesday bought 85,000 shares of the company's common stock on the open market for about US$2.4 million, at a time when the share price has significantly underperformed the U.S. transport sector.

Chief Executive Officer Doug Parker purchased 50,000 shares on the open market for US$1.4 million, while President Robert Isom bought 15,000 for US$416,250, according to regulatory filings with the Securities and Exchange Commission.

"These share purchases are not part of our compensation package. They were purchased solely because of the value we see in American today and over time," the executives said in a letter to American employees, which did not include the number of shares bought or at what price.

Chief Financial Officer Derek Kerr and three other executives bought 5,000 shares each for about US$138,800, the filings showed.

American, which has been hurt by the worldwide grounding of Boeing Co's 737 MAX planes, has been among the worst performing stocks this year in the airline industry.

The company's shares have fallen more than 9 percent so far in 2019, compared with an 8.8% rise in rival Delta Air Lines Inc's and 3.8% fall in United Continental Holding Inc's. The broader Dow Jones Transport Average index has risen about 10% during the same period.