The BBC reports that after two "hackers" spotted security holes in its website, United rewarded them with a million miles each.
One security expert said the scheme was a big step forward for online security.
"Schemes like this reward hackers for finding and disclosing problems in the right way. That makes the internet safer for all of us," said security consultant Dr Jessica Barker.
"Bug bounties are common in tech companies as they tend to understand online security a bit more, but other industries are catching up," said Dr Barker.
