A few considerations...
I think a large scale, unifying initiative, national to start and hopefully growing into an international phenomenon that is pro-peace would be cool.
Alright...a quick reminder on some logistics and a few suggestions (I am not part of the team organizing this in case there was any confusion. Already had one person contact me to say they had donated to "my" project.

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I don't think anyone has forgotten yet the struggles with wind and weather when it came to getting the full sized blimp into the air but they were many and even though we were in the south wind, fog and rain kept the blimp grounded a bit. I also helped coordinate some of the banner flying planes over the NH primaries and they too have logistical issues when it comes to wind. Basically, it is hard to coordinate specific timed events to coincide with these two forms of publicity but if you set yourself a window of a few days and relax you can usually make things happen..but it does reduce the cost efficiency of the project.
Unless something major has changed since 2008 there are strict no-fly zones enforced over most major cities and there are required clearances over tall buildings that the FAA mandates for blimps that can make blimp visibility for rallies difficult. Many airports in smaller cities cannot accommodate blimps. Another consideration when it comes to stress and cooperation is that most blimp companies are used to having a home base and flying out of it daily for days on end, not hopping from place to place across the country. Those are all important considerations.
Now, I think blimps can be a great source of publicity and news coverage when they do something new and interesting (as was the case with the Ron Paul blimp and as would likely be the case with a Peace blimp). There are a few factors though if you want national (vs bits of local) publicity...the blimp needs to be big, the rallies need to be big or there need to be a lot of them. One small blimp traveling around and being at rallies with 20 people each would probably not be very well covered by non-local news outlets.
As far as media goes even the Ron Paul Blimp required hundreds of phone calls and even more emails to get the media coverage that it did and that was pretty labor intensive. The point of that is, don't expect the media coverage to just "happen" no matter how cool the idea is.
When I was coordinating rallies for the Ron Paul Blimp during the height of his presidential campaign, while the money bombs were in full swing and interfacing with meet-up groups all around the cities where the blimp would be we were hard pressed to get more than a hundred people to a rally. The "peace" blimp has the potential (will get into this next) to tap into a much larger demographic than the RPblimp but are peace lovers organized enough to create large scale peace rallies (more organized than the RP grassroots was?) when the blimp comes or will an accompanying structure have to go into place on the ground ahead of the blimp to organize rallies from the ground up?
The message...already seeing "End the Fed" and Ron Paul said "X" quotes going up here. As most of Trevor's current fund raising connections seem to be within the freedom movement (I could be wrong here) this is an ideal place to start but everyone who wants to see this happen needs to realize that if you want funding and coverage to come from across the political and even international spectrum the message of the blimp needs to be kept simple and universal. It can't allude to vague concepts that the majority of folks don't understand, be an "in your face" to people who didn't support Ron Paul, be full of US constitution love, etc... Not that there is ANYTHING wrong with these concepts but they do not make for a universally appealing message that can raise big bucks via a ton of small donations.
Now, a question...so far who all is on the "Peace Blimp" team? I have worked with a good number of the people in this movement on various projects and would like to know that ethical people who have brought success and professionalism to previous endeavors are in charge before a lot of freedom movement money goes into it.
Oh and keeping the dove symbolism (in particular a dove holding an olive branch) may be a good idea as it is ancient and spans the traditions of many cultures and religions and it would be easy for people to create "grassroots" supporting posters, art, cool on ground items like this:
http://doveballoons.co.uk/ at rallies. Now if fund raising really starts getting into the millions it might be worthwhile to hire an ad agency, I talked to a very cool one while doing the blimp thing in SC, and have them design a new symbol