Making sure things go smoothly is the responsibility of Paul Fox, integration director for the T5 project Making sure that T5 works as part of the whole airport, and works well from the moment it opens is Paul Fox's preoccupation and will be for the next four years. A member of the Heathrow Airport Limited executive, he is integration director for the project.
'If we draw any lessons from other new airports around the world, it is to understand where things might go wrong, ' he says.
'We can't have Heathrow disrupted. As an internationally connected airport with so many operators, if we sneeze here the rest of the system catches a cold worldwide.'
The follow through from studying other new projects is that a rehearsal period is vital before opening; terminals that had one mainly avoided trouble.
T5 will have a six-month 'operational readiness period' during which time new staff will be put in place and trained. Security, safety, information and building systems will be tested and run through repeatedly. Baggage handling will be operated for real as will the retail outlets.
Fox emphasises that this is not commissioning but a separate, additional period so that operational problems show up clearly and can be identified and resolved. Contingency plans can be tried out and third parties, like primary occupier British Airways and the retail outlets, can build experience too.
Inserting this extra time in the schedule 'represents a significant investment, ' he concedes. 'But we have looked at it closely and know it is an investment we want to make.'
But long before systems can be tested, they have to be in place.
And the more closely they are designed to suit the final operations the better.
Fox's work has already begun, feeding into not only the design process but the complex interactive development of the brief led by Mike Forster.
'My job is to be an interface with that team because the operational strategies are a significant part of the input into the brief, ' he says.
'You could call me the glue between HAL and the T5 team.
Representing Heathrow as a stakeholder I attend the main strategic meetings for both bodies.'
He and his team work with the designers on issues like floor layouts and IT cabling.
And, of course, there are security questions and the requirements of Customs & Excise and the immigration service to consider. Special Branch and other police and security services are also involved and have to be integrated into the whole picture.
'We also want to find ways to make the passengers' experiences as 'seamless' as possible, ' says Fox. The team works especially closely with British Airways to achieve this.
Integration on a broader scale is important. Fox underlines that T5 is part of Heathrow as a whole, rather than a separate entity. As it comes on stream, it will have a major impact on the rest of the airport.
'Taking 27M passengers a year out of the other areas will hugely reduce the congestion at present, and also leave some big spaces.
That is a big opportunity for future re-organisation.'
At present, Terminals One and Two are pretty much for UK and European flights by BA and other airlines respectively, and Terminal Three is for long haul, though Terminal Four is perhaps more mixed.
But re-grouping of airlines in the other four terminals is under discussion, and whatever the outcome, it seems certain that in future the terminals will all operate with a mix of long, medium and short-haul 'feeder' flights.
'That helps reduce transfer times and easier flight changes, ' says Fox 'as well as better utilisation of the spaces.'