$planes{ $aid }[ n ]{ ... };

##</code><code>##

C:\test>junk53
Aircraft: 599 heading:  0.000
Aircraft: 591 heading: 90.000
Aircraft: 599 heading:  0.000
Aircraft: 591 heading: 90.000

##</code><code>##

#! perl -slw
use strict;
use Data::Dump qw[ pp ];

my @headers = split ' ', do{ my $raw = <DATA>; $raw =~ tr[",][ ]; $raw }; #"

my %planes;

while( my $line = <DATA> ) {
    $line =~ tr[",][ ]; #"
    my @fields = split ' ', $line;
    my $rowid = shift @fields;
    my $aid = shift @fields;
    my %row; @row{ @headers } = @fields;
    push @{ $planes{ $aid } }, \%row;

    next unless @{ $planes{ $aid } } > 1;

    my $lat1 = $planes{ $aid }[ -2 ]{ latitude };
    my $lat2 = $planes{ $aid }[ -1 ]{ latitude };
    my $dlat = $lat2 - $lat1;

    my $lon1 = $planes{ $aid }[ -2 ]{ longitude };
    my $lon2 = $planes{ $aid }[ -1 ]{ longitude };
    my $dlon = $lon2 - $lon1;

    my $y = sin( $dlon / 180 ) * cos( $lat2 /180 );
    my $x = cos( $lat1 /180 ) * sin( $lat2/180 ) - sin( $lat1/180 ) * cos( $lat2/180 ) * cos( $dlon/180 );

    printf "Aircraft: %d heading: %6.3f\n", $aid, atan2( $y, $x ) * 57.2957795;
}


__DATA__
"rowid","aircraft_id","actual_date_time","latitude","longitude","radio_altitude","ground_speed","thrust_engine_1","thrust_engine_2"
3828994,599,2012-11-04 14:00:00,51.47592545,-0.437049866,-9.0,2.0,0.044653355,0.041778761,1.74208527619370935228499282740898271690901934191164070390564,15.22092881857486030932218666006017736321211426212568671811012
3828995,591,2012-11-04 14:00:00,51.47598267,-0.435331702,-0.875,0.0,0.066208174,0.068682498,0.91309579395343765782284643054122415908645386540627114668956,4.89409068988509446645508839697462129412344644649063483492349
3828996,599,2012-11-04 14:00:01,51.47592545,-0.437049866,-9.0,2.0,0.044653355,0.041778761,1.74208527619370935228499282740898271690901934191164070390564,15.22092881857486030932218666006017736321211426212568671811012
3828997,591,2012-11-04 14:00:01,51.47598267,-0.435331702,-0.75,0.0,0.064970428,0.068682498,0.90550603857151443957938619839883126906356038703789731965392,4.92096836684002218971971504299700119099094370033875757916224
3828998,599,2012-11-04 14:00:02,51.47592545,-0.437049866,-9.0,2.0,0.044653355,0.041778761,1.74208527619370935228499282740898271690901934191164070390564,15.22092881857486030932218666006017736321211426212568671811012
3828999,591,2012-11-04 14:00:02,51.47598267,-0.435331702,-0.625,0.0,0.066208174,0.068682498,0.91309579395343765782284643054122415908645386540627114668956,4.89409068988509446645508839697462129412344644649063483492349