In separate cabins creates UCM requirement!
 

Now if they would just fix online booking to let me book my teenaged kids in coach and me and my wife in first on one reservation - otherwise my kids are unaccompanied minors which takes a forty-five minute phone call to take care of ... and the fares go up, and an online booking fee is added, and I lose the free checked bag with Economy Plus, ...

Oh man, THIS

My son turned 18 this year, so now he is the guardian on my daughter, so splitting up PNR's just got extremely easy for me again, but I have felt your pain for the past many years. We usually sit in the same class, but I pay with a mix of dollars and award miles, which produces the same results.

Unaccompanied Minors

This has nothing to do with how UA books. Your children are unaccompanied minors if they are not ticketed in the same cabin. Whether the tickets are issued in the same PNR or not is irrelevant. The requirement is a safety & security matter in case of emergency evacuation and a handling matter if you consider that at least as far as DHS rules go, passenger movement between cabins is prohibited on international flights destined to the US.

I can't conceive of booking kids into any cabin other than the one in which I am seated.

The last point, especially. But in any case, if you aren't there to care for your kids, which you can't be if you are sitting in different cabins, they are still, literally, unaccompanied minors, and I have no problem with that definition. I do definitely have sympathy for the case of sitting in the same cabin with kids booked on an award in a different PNR, with adults in cash (or vice-versa). There should definitely be a workaround for that (is there?)

International or big planes sure. Sitting in the last row of FC 4 C/D and them sitting in the first row of E+ in a E175 or a RJ700 is a totally different thing all together. Same could be said for most domestic single isle planes except maybe some of the stretches that have a lavatory between first and economy.

Back in the 70's, I flew by myself from DCA/BWI-FLL all the time, no paperwork, my mom would board with me, introduce me to the FA's and deplane. Now that takes mounds of paperwork. Hell, back then at FLL, you didn't even pull up to the gate, they let you out on the Tarmac with roll up stairs, that was the best part of the trip for an 8yo kid.

The unaccompanied minor policy goes up to age 15. I can certainly conceive of sitting in separate cabins with kids that are 13, 14, 15 years old.

Minor Traveling Reward Ticket Q
 

Not sure whether to post here or AC. Need to book one way for my 14 yo LAX to YVR nonstop. Was going to use miles from my United account. Flt is on AC. AC allows 14yo to travel alone, UA does not--must pay $150 UM fee. So is it possible to use miles to book her a ticket on AC with wrong birth year, and then call AC to change birth year? I've done this before with rev tickets, but not mileage?

Kids travelling alone is a touchy situation for the airlines. If you're caught lying you could lose your MP account and all mileage in it. Why don't you just be honest? Why don't you just conform to the rules of the airline whose benefits you're trying to use? The problem comes up during re-accommodation in case of AC cancellation. UA will have option of putting her on UA flights and they'll figure out pretty fast what the scam is when a 14 y.o shows up.

I thought UA's UM policy only is applied to UA metal. If the entire journey is on AC, UA can book a 14 year old and whatever policy AC has applies. I don't think you need to do this fancy workaround.
In other words, booking AC using UA miles is basically the same thing as UA acting as a travel agent. Any any travel agent selling a ticket on any airline has to be familiar with and abide by the rules and policies for the operating carrier, which is AC.

Read the section on unaccompanied minors at UA.com. They will only ticket an unaccompanied minor on UA/UAX metal. No codeshares. The problem is IRROPS since UA issues the ticket.

I think it's subject to interpretation. I read it as "UA's unaccompanied minor policy AND service does not apply to codeshare flights or flights on other airlines."

Seriously? How do you manage to come to that conclusion when the first sentence is: "Unaccompanied minors can only travel on nonstop flights operated by United or United Express"? The policy goes on to make it more clear - not on codeshares, not on partner flights. United will not issue a codeshare ticket for an unaccompanied minor. As the OP has already pointed out, he has gamed the system to avoid the rule.

Agreed. Any of us who try doing this with the right age would quickly find no other options besides UA/UAX metal.

Thanks for the feedback. Moot now, as I've booked using Aeroplan miles. However just to be clear, I called United and was told I could book a 14yo on the flight for Air Canada, without the UM fee, as AC policy applies, not UA.