United Airlines now allows frequent flyers to pool miles with 4 other people in a joint account

• United Airlines now allows frequent flyers to pool miles in a joint account.
• Miles pooled into the joint account can't be transferred back to individual accounts.
• JetBlue and Frontier previously launched similar miles-pooling programs.

United Airlines now allows frequent flyers to pool miles with four other people in a joint account, the airline said in a press release on Thursday.

United said in the press release that MileagePlus members can start combining their miles into a joint account so long as each person is a member of the loyalty program — but there is a catch.

Luc Bondar, the COO of United's MileagePlus program, told CNBC that miles pooled into the joint account cannot be transferred back into individual accounts.

How it works is that one MileagePlus member over the age of 18 — or what United calls the "pool leader" — can invite four other members to pool miles into the account, the airline said. The four other members can be of any age, per the press release.

Each member can then choose how many miles they want to contribute to the account, and there is no limit to how many miles they can pool together, United said.

Members can use these miles and redeem discounts when purchasing tickets on United's website and mobile app, per the press release. United did not immediately respond to a request for comment from Business Insider.

Previously, two other US airlines have launched similar miles-pooling programs. In November 2018, JetBlue announced it was allowing up to seven members of its TruBlue loyalty program to pool miles. In January, Frontier launched its "Family Pooling" program for up to eight members of its Frontier Miles loyalty program to pool miles.