<?php

$difference = (strtotime($row['Landing']) - strtotime($row['Take_Off']);

$hours = ceil($difference/60/60); // rounds the hours to the nearest hour.

$minutes = (($difference - ($hours * 60 * 60))/60); // rounds the remainder of the hours to the nearest minutes.

$time = $hours.":".$minutes; // puts a : between the hours and minutes.

?>