When you get a traffic citation in PA you have to respond within 10 days. This is what didn't happen and why the warrant was issued. PA citations do not have a hearing date generated automatically. You can plead guilty or not guilty by mail, though either way you have to come up with the original fine (and in fact an extra 5 bucks if you plead not guilty). There is some provision arrange to enter the not guilty plea in person if you can't afford to front the fine, but AFAIK this doesn't fly unless you really can't come up with the cash. Paying in the money is to insure your appearance at the hearing. Only after you enter a not guilty plea will the hearing be scheduled.
Some info on citations in PA here:
http://www.munley.com/traffic_violat...nsylvania.html
As far as the warrant goes:
What If I Do Not Respond To A Citation?
If you do not answer a citation within 10 days, you can be arrested. This arrest is usually made by a local constable. When the constable appears with the arrest warrant, you can avoid arrest by 1)paying the amount of the fine plus an additional $5 and costs as security for your appearance at hearing; or 2) pleading guilty and paying the fines and costs.
The constable will return the warrant and the security money to the district justice, who will then send out a notice of the date and time of the hearing to you and the police if a not guilty plea has been made. If you do not pay the security money to the constable, you can be arrested and taken before the district justice.
Doesn't sound too serious, can't imagine it affects your ability to fly. It'll mainly affect dealings in PA I would think. But you should get it taken care of. It looks like it'll just go away if you pay the ticket (follow the instructions included with the letter; I assume there were some), although it appears you can still have your day in court if you want. (Two days, really, at least: if you lose the first round, you can appeal to the next level with a brand new trial. When I fought my ticket the district justice lowered my offense to one with no points and a lower fine; I got a refund of the fine difference in the mail.) It doesn't sound like you have time for this though.