I've been wondering similar things!

Typically, I've bought my "high season"/"high demand" Christmas tickets already a month ago -- the weekend before Christmas outbound, weekend after for the return. In the past, I've been able to snag them for around $600 early enough.

I've been running fare searches literally every day since August and the fares haven't dropped below $1,200 for my dates. While I'm not panicking yet... I am getting a little nervous! Typically the lower fare inventory has been opened up (and sold out!) a long time ago. As far as I can tell, UA hasn't opened up the lower fare buckets yet.

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"There are those who travel, and those who travel well."