gistfile1.txt

lat_filtered <- airport$lat[airport$FAA == input$Input1]
lng_filtered <- airport$lng[airport$FAA == input$Input1]
        
        airport <- filter(airport, Country=="United States")
        airport <- inner_join(airport, major, by="Name")
        
        for(i in 1:nrow(airport)) {
            if(airport$Country[i] == "United States" & airport$FAA[i] != input$Input1) {
                route <- gcIntermediate(c(lng_filtered, lat_filtered), 
                                        c(airport$lng[i], airport$lat[i]),
                                        n = 200, addStartEnd = TRUE)
                route <- as.data.frame(route)
                if(!is.null(route))
                    routes[[length(routes)+1]] <- route
            }
        }
        
        addRoutes <- function(map, x, ...) {
            for(i in 1:length(x)) {
                tryCatch(map <- addPolylines(map, lat = x[[i]]$lat, lng = x[[i]]$lon, ...),
                         error = function(e) map,
                         finally = map)
                
            }
            return(map)
        }