Originally Posted by
LondonElite
You could buy a UA/AA/DL club membership, but that would limit you to that airline's lounges, when flying on those airlines.
That's not entirely true. Although a Club membership would limit OP to a specific airline (or Alaska's if AA/DL), there's no requirement that OP be flying on those airlines. If flying to/from smaller domestic airports, a UA/AA/DL lounge might be all that's available.
That being said from a value perspective, these club memberships still tend to be a bad deal.