Last night, Delta Air Lines added another $10 roundtrip increase to this past weekend’s increase of up to $50 roundtrip. That first hefty hike was initiated by United, and then all the legacy carriers joined in. But this latest increase from Delta, well, I am trying to think of a word other than “unprecedented” so I guess I’ll start using “remarkable.” And that’s because, in 6- years of tracking airfares, I have never seen an airline fire out a system wide increase on anything but Thursday or Friday! Keep reading…

This increase just doesn’t break the mold, it shatters it — the ninth increase attempt this year (and 6 of the previous 8 in 2008 were “sticky”).

With this latest increase, Delta has raised prices on over 16,500 city pairs in their route system.

Meanwhile, here is a rundown of some factoids related to this weekend’s “up to $50 roundtrip” increase (not including Delta’s increase last night); these stats areacross all airlines:

• 82,000city pairs with $10-roundtrip increase
• 2,562 city pairs with $20-roundtrip increase
• 140,000 city pairs with $30-roundtrip increase
• 68,000city pairs with $50-roundtrip increase

AirTran, jetBlue, Alaska and Frontier all participated (in varying levels) in matching this increase.

In the past few days, I’ve pondered “when the other shoe was going to drop” — today, with the Delta and United announcements of cutbacks in capacity (and also labor for Delta)– I am pretty sure the laces are at least untied on that shoe. Whether legacy airlines merged or not — cutbacks were inevitable, especially in an environment of record fuel prices and probable softening in demand related to looming economic pressures.

Domestic air travelers have no choice but to ride out this “storm” of increases — savvy travelers can “hedge” these increases by shopping earlier and being more flexible — and there will be plenty of airline ticket deals to be had in the coming year for those that can force themselves to change their air travel shopping habits. Airlines are intimately aquainted with our travel shopping habits and will be charging hefty premiums for those that continue normal patterns.

And yes, I’ll keep watching…and keep you informed.