In order for this API to work, the Origin and Destination Airports must be distinct.

Here is sample output for JFK (New York City) and YYZ (Toronto):

{ "type": "FeatureCollection", "features": [ { "type": "Feature", "properties": { "fir": "KZNY", "country": "USA", "fir_name": "FIR NEW YORK", "dist_km": "332.74", "dist_nm": "179.66", "sequence": 1 }, "geometry": { "type": "LineString", "coordinates": [ [ -73.7786925, 40.63992778 ], [ -73.8493159601456, 40.680166316078164 ], [ -73.92002468923548, 40.72036176843577 ], [ -73.99081881976335, 40.76051402379085 ], [ -74.06169848396787, 40.800622968624715 ], [ -74.13266381382869, 40.84068848918186 ], [ -74.20371494106244, 40.88071047147002 ], [ -74.27485199711889, 40.9206888012602 ], [ -74.34607511317681, 40.96062336408667 ], [ -74.4173844201401, 41.00051404524699 ], [ -74.48878004863356, 41.04036072980204 ], [ -74.56026212899894, 41.0801633025761 ], [ -74.63183079129088, 41.119921648156826 ], [ -74.70348616527262, 41.159635650895375 ], [ -74.77522838041202, 41.19930519490638 ], [ -74.84705756587728, 41.23893016406813 ], [ -74.91897385053277, 41.2785104420225 ], [ -74.99097736293486, 41.318045912175144 ], [ -75.06306823132758, 41.35753645769551 ], [ -75.13524658363836, 41.39698196151696 ], [ -75.20751254747385, 41.43638230633687 ], [ -75.27986625011542, 41.475737374616706 ], [ -75.35230781851487, 41.515047048582176 ], [ -75.42483737929017, 41.55431121022326 ], [ -75.49745505872086, 41.59352974129448 ], [ -75.57016098274377, 41.63270252331486 ], [ -75.64295527694847, 41.67182943756822 ], [ -75.7158380665729, 41.71091036510321 ], [ -75.78880947649874, 41.749945186733505 ], [ -75.86186963124699, 41.788933783037955 ], [ -75.93501865497329, 41.827876034360756 ], [ -76.0082566714635, 41.86677182081162 ], [ -76.08158380412891, 41.90562102226596 ], [ -76.15500017600178, 41.944423518365085 ], [ -76.22850590973052, 41.98317918851635 ], [ -76.30210112757511, 42.021887911893415 ], [ -76.37578595140238, 42.06054956743644 ], [ -76.44956050268124, 42.099164033852276 ], [ -76.52342490247788, 42.13773118961472 ], [ -76.5973792714511, 42.176250912964704 ], [ -76.67142372984738, 42.214723081910634 ], [ -76.74555839749604, 42.253147574228514 ], [ -76.81978339380451, 42.291524267462265 ], [ -76.89409883775328, 42.329853038924036 ], [ -76.96850484789101, 42.36813376569435 ], [ -77.01770304732813, 42.39338284652019 ] ] } }, { "type": "Feature", "properties": { "fir": "KZOB", "country": "USA", "fir_name": "FIR CLEVELAND", "dist_km": "211.76", "dist_nm": "114.34", "sequence": 2 }, "geometry": { "type": "LineString", "coordinates": [ [ -77.01770304732813, 42.39338284652019 ], [ -77.04300154232969, 42.40636632462253 ], [ -77.11758903873954, 42.444550592326884 ], [ -77.19226745434405, 42.482686445195036 ], [ -77.26703690591503, 42.52077375938422 ], [ -77.34189750976749, 42.55881241082162 ], [ -77.41684938175453, 42.596802275204695 ], [ -77.49189263726235, 42.63474322800143 ], [ -77.56702739120503, 42.67263514445079 ], [ -77.6422537580194, 42.71047789956297 ], [ -77.71757185165987, 42.748271368119816 ], [ -77.79298178559328, 42.786015424675185 ], [ -77.86848367279354, 42.82370994355522 ], [ -77.94407762573648, 42.861354798858905 ], [ -78.01976375639457, 42.89894986445831 ], [ -78.0955421762315, 42.936495013999014 ], [ -78.17141299619699, 42.9739901209006 ], [ -78.24737632672138, 43.01143505835697 ], [ -78.32343227771018, 43.048829699336856 ], [ -78.39958095853872, 43.08617391658416 ], [ -78.47582247804675, 43.1234675826185 ], [ -78.55215694453287, 43.160710569735606 ], [ -78.62858446574914, 43.197902750007785 ], [ -78.70510514889556, 43.235043995284414 ], [ -78.78171910061444, 43.27213417719243 ], [ -78.85842642698495, 43.30917316713676 ], [ -78.93522723351748, 43.34616083630093 ], [ -79.01212162514801, 43.38309705564749 ], [ -79.08910970623249, 43.419981695918544 ], [ -79.1661915805412, 43.45681462763632 ], [ -79.17263590701272, 43.45988592024664 ] ] } }, { "type": "Feature", "properties": { "fir": "CZYZ", "country": "Canada", "fir_name": "FIR TORONTO", "dist_km": "44.08", "dist_nm": "23.80", "sequence": 3 }, "geometry": { "type": "LineString", "coordinates": [ [ -79.17263590701272, 43.45988592024664 ], [ -79.24336735125299, 43.49359572110368 ], [ -79.32063712094967, 43.530324846404696 ], [ -79.39800099161015, 43.56700187340519 ], [ -79.47545906460478, 43.603626671753275 ], [ -79.55301144068949, 43.640199110880026 ], [ -79.63065822, 43.67671906 ], [ -79.63065822, 43.67671906 ] ] } } ] }