Arc.js

HTML

<script src="https://api.tiles.mapbox.com/mapbox.js/v2.1.9/mapbox.js"></script>
<link rel="stylesheet" href="https://api.tiles.mapbox.com/mapbox.js/v2.1.9/mapbox.css">
<script src='https://api.tiles.mapbox.com/mapbox.js/plugins/arc.js/v0.1.0/arc.js'></script>
<div id='map'></div>

CSS

body { margin:0; padding:0; }
#map { position:absolute; top:0; bottom:0; width:100%; }

JavaScript

L.mapbox.accessToken = 'pk.eyJ1IjoiYW5jZXN0cnltYXBib3giLCJhIjoiNllqcGhKYyJ9.p9QKjx4kc2E_55jLTmDw0Q';
var map = L.mapbox.map('map', 'mapbox.streets')
    .setView([42.87596410238254, -100.546875], 3);

// Start and end points, in x = longitude, y = latitude values
var start = { x: 0.1275, y: 51.5072 };
var end = { x: -77, y: 39 };
var generator = new arc.GreatCircle(start, end, { name: 'Seattle to DC' });
var line = generator.Arc(100, { offset: 20 });

var line_options = {
    color: '#60527E',      // Stroke color
    opacity: 1,         // Stroke opacity
    weight: 3,         // Stroke weight
};

L.mapbox.featureLayer({
    // this feature is in the GeoJSON format: see geojson.org
    // for the full specification
    type: 'Feature',
    geometry: {
        type: 'Point',
        // coordinates here are in longitude, latitude order because
        // x, y is the standard for GeoJSON and many formats
        coordinates: [
          -77.03221142292,
          38.913371603574 
        ]
    },
    properties: {
        title: 'Arrival',
        description: '1898 • New York City, New York, United States',      
        'marker-size': 'medium',
        'marker-color': '#60527E',
        'marker-symbol': 'circle'
    }
}).addTo(map);

L.mapbox.featureLayer({
    // this feature is in the GeoJSON format: see geojson.org
    // for the full specification
    type: 'Feature',
    geometry: {
        type: 'Point',
        // coordinates here are in longitude, latitude order because
        // x, y is the standard for GeoJSON and many formats
        coordinates: [
          .012234, 
          51.5072
          
        ]
    },
    properties: {
        title: 'Departure',
        description: '1898 • London, England, United Kingdom',      
        'marker-size': 'medium',
        'marker-color': '#60527E',
        'marker-symbol': 'circle'
    }
}).addTo(map);



L.geoJson(line.json(),line_options).addTo(map);