thanks for the replies - I was just wondering why pilots don't slow down and save a bit of fuel if they know they're going to be early, instead of arriving unhelpfully ahead of schedule (over the heads of a few million sleeping Londoners in a noisy 747). At other times of day, of course being early is usually a bonus for the customer. And of course, getting down on the ground while you can is better & safer than arriving on time and then being held - waiting for a landing slot (using up more fuel and making more noise). And the pilot and crew possibly want to put their feet up.