print OUTFILE "$line_1";

	my $meter = $length_1;

	if (defined $aircraft_id_1){

	

		################### OPEN THE SECOND INFILE ############################
	

		open(INFILE_2,"<${file_2}") or die "Can't open ${file_2} : $!";

		#################################################################
			
		while (my $line_2 = <INFILE_2>){
			chomp($line_2);
			my @Elements_2 = split(/;/, $line_2);

			# warning : in this file, the aircraft_id looked for is in the first column
			my $aircraft_id_2 = $Elements_2[0];

			# print STDOUT "the aircraft_id in the resemblance_criterion_file is : $aircraft_id_2\n";

				if ($aircraft_id_1 eq $aircraft_id_2){
				print OUTFILE ";$line_2\n";
				}
			}

		close INFILE_2;
		}