library(maps)
library(geosphere)
xlim <- c(-164, 20)
ylim <- c(12, 71)
airports <- read.csv("http://web.me.com/bradthiessen/airports2.csv", header=TRUE)
flights <- read.csv("http://web.me.com/bradthiessen/flights.csv", header=TRUE, as.is=TRUE)
pal <- colorRampPalette(c("#6588A4", "#44596C"))
colors <- pal(100)

map("world", col="#DCDCDD", fill=TRUE, bg="white", lwd=0.05, xlim=xlim, ylim=ylim)

fsub <- flights[flights$airline == "AA",]
fsub <- fsub[order(fsub$cnt),]
maxcnt <- max(fsub$cnt)
for (j in 1:length(fsub$airline)) {
	air1 <- airports[airports$iata == fsub[j,]$airport1,]
	air2 <- airports[airports$iata == fsub[j,]$airport2,]

	inter <- gcIntermediate(c(air1[1,]$long, air1[1,]$lat), c(air2[1,]$long, air2[1,]$lat), n=100, addStartEnd=TRUE)
	colindex <- round( (fsub[j,]$cnt / maxcnt) * length(colors) )

	lines(inter, col=colors[colindex], lwd=1.0)
}