They can't just "annul" it. Barring another bankruptcy and getting contracts flushed down the toilet. The flow is contractual and arbitrated awards. It would be like them saying OK, I know your contractual pay rate is $80/hr but we just aren't going to pay you that anymore because it doesn't suit our needs.. I guess they "could" do that whenever they feel like it, but it will go to court, and they will very likely lose and have to make it right with damages, back pay etc...
They have not ever thrown out any flow yet.. The old letter 3 flow from MANY years ago was convoluted and had lots of problems and delays, and then we had flowbacks from AA come back down to Eagle due to the massive AA furloughs around 9/11 that lasted until just a few years ago. Also AA didn't hire anyone for over a decade up until 2013 (so of course there was no flow through that time for all those years, and it's why people on the forums always say "look" how long the Envoy flow is.. without understanding WHY.. NO NEW HIRES AT AA FOR 13 YEARS!!).. But NOW, since the AA furloughs have been recalled (one last batch left to go if they want to return) and hiring has resumed in 2013.. The flow has been working and they are honoring it (actually better then they are required to do). If you look at the above chart, hiring this year has been kinda slow at AA.. but they have still given us 65% of the class slots for the year. They are only required to give us 50% of new hire positions. Next year AA hiring projections are around 700 I believe. Someone correct me If I'm off a bit here.. Can't remember exactly what that announcement said.
There is more good info about flow and movement further down the page on the other Envoy thread:
http://www.airlinepilotforums.com/re...signments.html
I really don't know of any other flow over the last decade, since I have been in this industry that was ever just "annulled". Compass/Northwest flow is being honored by Delta.. Piedmont/USair to AA.. PSA or Endeavor isn't really a flow, just a preferential interview.. What other one's is there?