PostgreSQL query for calculating possibility of flights between airports

check_possibility_of_flights_between_airports.sql

select 
       -- `distinct on` statement is required to exclude duplicate lines with return flights  
       distinct on (least(depart.arport_code, arrival.airport_code)
                    , greatest(depart.arport_code, arrival.airport_code))
    depart.arport_name
    , arrival.airport_name
    , 6371 -- Earth radius
      * acos(-- sin(latitude_a) * sin(latitude_b)
                  sin(depart.coordinates[0]) * sin(arriv.coordinates[1]) 
                  -- cos(latitude_a) * cos(latitude_b)
                  + cos(depart.coordinates[0]) * cos(arriv.coordinates[1])
                    -- cos(longtitude_a - longtitude_b)
                    * cos(depart.coordinates[1] - arriv.coordinates[1])                                                                   
    ) as fact_range
    , craft.range as craft_range
from flights as f
    inner join airports_data as depart on depart.airport_code = f.departure_airport
    inner join airports_data as arriv on arriv.airport_code = f.arrival_airport
    inner join aircrafts_data as craft on craft.aircraft_code = f.aircraft_code
where 
                                                                    
    craft.range > (6371 -- Earth radius
      * acos(-- sin(latitude_a) * sin(latitude_b)
                  sin(depart.coordinates[0]) * sin(arriv.coordinates[1]) 
                  -- cos(latitude_a) * cos(latitude_b)
                  + cos(depart.coordinates[0]) * cos(arriv.coordinates[1])
                    -- cos(longtitude_a - longtitude_b)
                    * cos(depart.coordinates[1] - arriv.coordinates[1])                                                                   
    ))
;