function animate() {
var flights = {
    100: ["travel-svo", "travel-svo"],
    600: ["travel-fra", "travel-fra", "travel-fra", "travel-fra", "travel-fra",
             "travel-fra", "travel-fra", "travel-nap"],
    620: ["travel-ams", "travel-ams"],
    700: ["travel-lhr", "travel-lhr", "travel-lhr", "travel-lhr", "travel-lhr"],
    710: ["travel-cdg", "travel-cdg", "travel-cdg", "travel-cdg", "travel-cdg"],
    805: ["travel-gva"],
    810: ["travel-vie", "travel-vie", "travel-vie", "travel-vie"],
    850: ["travel-ams", "travel-ams", "travel-ams"],
    855: ["travel-svo"],
    930: ["travel-beg", "travel-beg"],
    935: ["travel-muc", "travel-muc", "travel-muc"],
    945: ["travel-sof", "travel-sof"],
    950: ["travel-fco"],
    955: ["travel-cdg", "travel-cdg", "travel-cdg", "travel-cdg", "travel-cdg",
             "travel-cdg", "travel-cdg"],
    1010: ["travel-mad", "travel-mad", "travel-mad", "travel-mad", "travel-mad"],
    1015: ["travel-svo", "travel-svo"],
    1025: ["travel-zrh"],
    1030: ["travel-dxb", "travel-dxb", "travel-arn"],
    1035: ["travel-fra", "travel-fra", "travel-fra", "travel-fra", "travel-fra",
            "travel-fra"],
    1040: ["travel-led", "travel-led"]
};

var circle = function(coef, flight_id) {
    var svgns = "http://www.w3.org/2000/svg";
    var svgDocument =document;
    var motion = svgDocument.createElementNS(svgns,"animateMotion");
    var shape  = svgDocument.createElementNS(svgns, "circle");

    motion.setAttribute("begin", "path_ani.end");
    motion.setAttribute("dur", "10s");
    motion.setAttribute("path", document.getElementById(flight_id).getAttributeNS(null, "d"));
    motion.setAttribute("xlink:href", "#" + flight_id);

    shape.setAttributeNS(null, "r",  1*coef);
    shape.setAttributeNS(null, "fill", "1f78b4");
    shape.setAttributeNS(null, "stroke", "1f78b4");
    shape.setAttribute("id", "airplane-" + flight_id);
    shape.appendChild(motion);
    document.getElementById("airplanes").appendChild(shape);
}
setTimeout(function() {
    var time = 100;

    var interval = setInterval(function() {
        var f = flights[time];
        var counts = {};

        if (f) {
            // count unique items
            for(var i = 0; i < f.length; i += 1) {
                var num = f[i];
                counts[num] = counts[num] ? counts[num]+1 : 1;
            }

            for (var flight in counts) {
                circle(counts[flight], flight);
            }
        }
        time += 5;
        // stop
        if (time > 1040) {
            clearInterval(interval);
        }
    }, 50);
}, 12000);