United posted on Milepoint that they will no longer offer extra award space for three-cabin first class flights starting February 1.

I wanted to let you know about a change we’ll be making to the way we allocate MileagePlus award inventory for United Global First and United First on 3-cabin aircraft. As many of you know, we currently use the same fare class (ON) for both upgrades and Saver travel awards redeemed from MileagePlus Premier Platinum, Premier 1K and Global Services accounts. A consequence of this pairing has been fewer seats being available for upgrades.

To remedy this imbalance, we will begin using ON exclusively for upgrades into United Global First and United First on 3-cabin aircraft effective February 1, 2013. Having a dedicated fare class for these upgrades will enable us to offer differentiated availability. To accommodate this change, we will no longer offer a dedicated fare class for Saver travel awards redeemed from MileagePlus Premier Platinum, Premier 1K and Global Services accounts. Instead, the inventory once used for ON class will be allocated to O class, which will become the sole booking class used for Saver Awards in United Global First and United First on 3-cabin aircraft.

Between now and January 31, ON will still be used for new Saver Award bookings from Platinum, 1K and Global Services accounts, and any flights booked prior to this change will not be impacted. We’ll also continue to offer better access to Saver Awards in United First (on 2-cabin aircraft), United BusinessFirst and United Business for Premier Platinum members and above, and better access to Saver Awards in United Economy for all Premier members.

Platinum elites and higher currently get to use the upgrade bucket for redeeming awards on three-cabin first class flights, which is mostly international (“United Global First”) but occasionally domestic flights with 3-cabin aircraft.

United says this means “fewer seats being available for upgrades” which I guess is true, if their elites use miles to claim these seats as awards then the inventory isn’t being used for upgrades. That’s not obviously a problem but United thinks that it is. So they’re going to take away this benefit.

There will still be extra elite award space for two-cabin first class flying and for United’s international business class.

This seems strange to me, the idea of ‘protecting’ United’s 3-cabin international first class product from elites using miles, thinking they can sell more business class seats and then let those customers upgrade into first — as though United’s 3-cabin first is meaningfully better than ex-Continental two-cabin business. It’s a decent though not world standard seat, it’s a good although not world standard entertainment system, and it’s way below par food, service, and amenities (even with the recent introduction of sleep amenities).

As Wandering Aramean wrote, “If this is the only downgrade in the new year I’ll take it. But definitely a downgrade.”

I’ve found this space to be useful for securing awards on United’s toughest flights, like Australia and Hong Kong flights. Awards will be much tougher to get for top elites.

Although — and this is truly stating the obvious — it only affects a very limited subset of United’s 80 million or so members of MileagePlus.