Bagso said;
[if] a 747 did get into Northolt, it would never get out !!!!!!
Boeing's performance charts show that a 747-200 with GE CF6-50E2 engines can take off from about a 5,600ft or 5,700ft runway at a weight of about 635,000lbs (it's difficult to be precise reading the info from their charts). Northolt's runway is 5,545 ft so it's too short but not by much. I don't know the precise performance figures for Air Force One but taking off from a short runway like Northolt's is not quite as improbable as it might at first appear, especially as it was only flying to Belfast. Whether the runways and taxiways could cope with the weight and size of a 747 is another matter.
Maybe they could fit some sort of steam catapult system at Northolt to help shorten Air Force One's take-off roll
. Or, beter still, let him use Fairford.