OK! “tweak” might conjure up a variety of mental images, but in this case its one airline pinching the clown nose of another with audible honk.
The “tweak” manifests itself when an airline fires off a cheap airfare into one of it’s competitors hub cities (those airports have the most non-stop flights) .
Take for example Airtran’s “tweak” of Northwest Airlines this morning…
At 10am Airtran filed an airfare between Memphis and Minneapolis (both are Northwest Hubs) for $69 each way — $50 less than the current cheapest price on Northwest (Northwest has the only daily non-stop).
So why do airlines employ the “tweak”?
Airlines watch each other closely. They certainly don’t want to be blindsided by another airline and are fiercely protective of their market share between certain cities. So in this case it is most likely that Airtran doesn’t like something that Northwest “did” to them out of Atlanta (Airtran’s Hub).
This actually happens all the time. We get to see this all day long as we process the airfare feeds 8 times a day directly from the airfare clearinghouse in Washington D.C.
If you happen to be one of the lucky air shoppers that catches a “tweak”, count yourself lucky or if you are more into knowing EXACTLY when a it occurs — sign up the FareCompare.com airfare email alerts — you’re bound to get “tweaked” sooner or later 
[...] Many times an airline will show its displeasure with another airline by posting super cheap fares in a competitor’s top city. I show you a classic example of this in my blog post on How Airlines “Tweak” Each Other. [...]
It would be interesting to see a list of the “hubs” for every airline, so we would know which cities were potential players in airline “tweaks.”
[...] week I coined a new air travel term called the “Tweak” (where airlines not so subtly lower prices on their competitors most prized [...]
[...] of these fares will only be around for a short period because they are “tweaks”, others are just plain “Crazy [...]
I am not refering to a website…I am hoping you can tell a first time traveler how to use your website to get a quote.
Is there nothing I can do when I have a non refundable ticket in one name for travel to a wedding and another family member, (with the same last name – only need to change the first name) could use the ticket?