color lines by gradient

airplanes.sql

create table flight_segments as
SELECT hexid,start_time,end_time,callsign,point,
   -- take a substring if the length reamining in the segment is greater than 5280 feet (1609.34 m)
   -- otherwise take the remainder
   ST_LineSubstring(geom, 1609.34*n/length,
   CASE
     WHEN 1609.34*(n+1) < length THEN 1609.34*(n+1)/length
     ELSE 1
   END) as geom
FROM
   (SELECT hexid,start_time,end_time,callsign,point,
   -- reverse the vertex order so that the upstream end of each  
   -- linestring will be the remainder
   ST_LineMerge(ST_Reverse(geom)) AS geom,
   ST_Length(geom::geography) As length
   FROM flights ts
   WHERE ST_Length(geom) > 0
   ) t
CROSS JOIN generate_series(0,1000) n -- 10000 is arbitrary, but must be greater than the number of segments you're getting
WHERE n*1609.34/length < 1;