I am on BA239 in July to Washington and it is due to leave at 17:10. I have looked over the history of that flight and it appears to always leave late with the delay between 1 hour and 4 hours. Is there any reason why there is such long delays. I have tracked the flights and they plane appears to be late every day inbound from San Francisco or Vancouver. There is still over a 3 hour turnover to get it back on schedule but it doesn't appear to be able to get back on time. I'm mainly asking as there is no point in me getting to LHR at 2pm if the plane isn't going to take off till 8pm or later.