As far as i can tell, the last time we had an air traffic slow-down after 9/11 we witnessed the following:

1. "Future shape and size". This ultimately led to the significant pull back from LGW, reduction in average plane size (e.g. 319s instead of 320s) withdrawal from the regions (not sure if that was part of the same strategic review though), and ruthless culling of many routes long and short haul.

2. There were extra miles galore to be had for loyal members, which got replaced with bottles of wine as the traffic situation improved. Interestingly, extra miles offers (lots of miles as opposed to a small trickle) have just reappeared for the winter season

3. Lots of good ex LIS fares most of which have pretty much disappeared in the past 2-3 years.

I could imagine more of the same if we have another slow-down.