Yesterday morning (Thurs.) in the 10am EDT domestic airfare distribution, AirTran Airways increased airfares by $6 and $10 roundtrip (based on distance) – and this was across the bulk of the carrier’s route system.

A few hours later, American and Delta/Northwest matched on overlapping routes, while Continental took it a further step and matched on the bulk of its route system – and by yesterday evening, United and US Airways matched across the bulk of their respective route systems.

This increase marks what appears to be well on its way to the 6th successful hike of 2009 – and all of these hikes have come since June.

Holiday travelers did get a bit of a break – with numerous holiday/winter sales out this week – and then, along came the airfare hike.

The volatility of yesterday’s airfare filings underscores the airlines’ continuous tinkering as they hone in on price points that reflect an up-tick in demand while trying not to scare off skittish travelers.

It’s also one more wakeup call for procrastinating holiday air travelers – if you haven’t purchased your tickets, get going now.