Update 3/26/24: Tech glitch has now been resolved and this is working again.
Update 3/22/24: A few hours after launch this was pulled from the United website. United is saying this is due to a technical glitch and they hope to have it back soon.
Update 3/21/24: This has now been confirmed by United. Details are as follows:
Pool leader must be 18+ but can invited up to 4 other people to join of any age (total of 5 people in the pool)
You can only participate in one miles pool at a time
You need to wait 90 days between leaving a pool and joining a new one. If your pool was full (5 people) and one person leaves, you need to wait 90 days before adding a new person
Pooled miles can only be used to book United and United Express flights. Pooled miles cannot be used to purchase upgrades, seat assignments, onboard food and beverages, inflight Wi-Fi access or anything else
Contributing miles to a MileagePlus miles pool will not affect an individual member’s Premier® status.
Only members who travel on a ticket using pooled miles will earn any eligible Premier qualifying points (PQP), not the member who contributed them. Members cannot pool PQP, Premier qualifying flights (PQF), PlusPoints, or TravelBank cash.
Restriction of this only being able to book United an United Express flights will kill the excitement for many, but still an improvement.
Original post: According to trusted aviation insider JonNYC United Airlines will introduce mileage pooling. Members will be able to join one pool and add miles to a collective account, the pool leader can then determine how those miles are used. Aeroplan previously offered this but has suspended family sharing, whereas JetBlue, British Airways & others all offer variations of this. I assume there will be some preventative measures that aim to stop things like selling miles and accumulating orphaned points (e.g transfers of at least 1,000 miles).