This idea was spawned by reading The Survival Blog found via the Carnival of Cordite #27 via Say Uncle.
The writer of the Survival blog suggests having a retreat special prepared for a catastrophic situation. The idea makes sense. There are many pros to this approach. You can pick the location, which means that it can be picked based on certain specific criteria. Water sources, defensibility, climate, or any other sort of criteria could be used in finding your retreat. You can also prestock your retreat with the goods that you will need to live a long, fruitful, and happy existence in a post apocalyptic world.
The problem with this I that most people cannot afford an extra house you do not live in. That is also one reason why the writer suggests living there year round, just in case. (Personally, my girlfriends parents and my parents both live in excellent retreat locations, if they were prepared ahead of time.) He also mentions the option of trying to get our of town when disaster strikes, which in some situations would work just find and in others you will just be apart of the herd, and warns against it. Basically, if you are not already at your retreat, you cannot guarantee your arrival.
The problem is getting to your retreat through choked or even dangerous highways (Remember social order has broken down). If you run out of gas there may be none, you may run over homemade spike strips set out by bandits, you could be stopped by government roadblocks, or any number of things could happen.
Though what if you were able to raise you chances of getting to your retreat location drastically...
If you were able to do that, it would become much more feasible to live where ever you want and just leave town when disaster strikes. My idea would be to use a Ultralight to fly to your retreat location.
This has some pros. It bypasses the roads, which is where the city folks are going.
This also has some con's and many unknowns. You could be shot down, but with proper flying you might be able to limit you exposure to radar and ground based bullets, of course if you meet another enemy flying object you are dead.
It may also be dependent on weather. If a meteor strikes or volcano erupts, the weather could be severely disrupted.
You will also need a certain amount of clear space to get off the ground.
As far as unknowns go, how much weight can you carry, how far can you fly, can you fly at night with out running into anything. Over all I think the idea has potential, but it is one of those things you cannot test well due to freaking government interference.
NOTE: In a zombie invasion, I think an ultralight would work well. Weather would not be a concern. Zombies do not shoot back, at least at first. And you would not have to fly at night. The only problem would be finding enough space to take off with. Though, if you did a motorized landing, you would attract all zombies in the area.