AP) — The project will cost 20 million pounds ($31 million), process 37,000 bags and deal with 10,000 or so athletes. But don’t blink, because you might miss Heathrow’s Games Terminal: After three days, it will disappear.

So why would Heathrow build an expensive special terminal whose only goal in its 72 hour lifespan is to send Olympians on their way home? It isn’t as if Heathrow doesn’t know a thing or two about crowds. This is Europe’s busiest airport, after all, and one of the busiest on the planet.

But research suggested that departures – not arrivals- are what cause problems for Olympic airports. That’s because athletes filter in over time, arriving for training and acclimation sometimes months before the games. But the bulk of them leave Aug. 13, the day after the Closing Ceremony.

First and foremost on the minds of organizers is security for the athletes. Then there’s the athletes’ needs: It just didn’t seem right to have Olympians wait in line like the average frequent flier.

“Athletes are at the top of their professions,” said aviation industry consultant Chris Yates. “Do they really want to be hanging out with you and I?”

But there’s also just the crush of everyone racing for the doors once the party is over. Heathrow could have lumbered along- processing as many as 137,800 passengers, athletes included – but doing that would have increased the burden on everybody leaving after the games.

“It’s not just about the athletes,” said Nick Cole, who’s heading the Olympic project for the airport. “We want everyone using it to have a fantastic experience.”

Cole, a former army officer, has been building his team and vision for the last two years. It wasn’t all about construction. He’s spent a lot of time persuading the 200 or so companies at Heathrow to meld their operations, if only briefly.

Whenever you get on or off a plane, dozens of different companies get involved in bits and pieces of the travel experience. One takes care of bags; another tickets, and so on. Cole had to persuade the individual companies to think about it like the 4 x 100 relay. There’s a baton. If you drop the baton, you lose.

That is especially true about the Olympics. People need to be happy. And if the bags of the athletes and Olympic functionaries take forever to get checked, and they wait for hours to get through security, thousands of reporters will be handy to record every gripe.

Those reporters will note that Heathrow has had many troubles in the past few years. There was baggage chaos at the glittering new Terminal Five when it opened in 2008. There was the bickering and finger pointing between Heathrow operator BAA and the airlines after the failure to quickly remove snow in 2010, stranding Christmas travelers.

Meanwhile, troubles remain in processing arrivals. Only a few weeks ago, the lines at border control were so long that a new national scandal emerged. The troubles even touched some of the “Olympic Family” – people Heathrow is anxious to impress. International Olympic Committee member Barbara Kendall, a windsurfer from New Zealand who won gold in Barcelona 20 years ago, openly criticized the airport on her Twitter feed. Kendall wrote: “Heathrow Airport Immigration is a nightmare!! took me 2 hours to get through and it is not Olympic time yet.”

It’s worth the multi million pound expense to keep these people on your side, said Ben Vogel, the editor of IHS Jane’s Airport Review.

“It is not the start of the Olympics that generates the most concentrated demand but rather the 48-hour period following the closing ceremony, when everybody wants to get home as quickly as possible,” Vogel said. “It does make sense to prepare … otherwise there may well be embarrassing delays that could cost more than 20 million pounds.”

Cole had an “aha!” moment when visiting the 2010 Winter Olympics in Vancouver, and noted how organisers effortlessly channeled thousands of passengers by designating a single terminal for the task. Heathrow is too busy to hand over one terminal at any time – never mind three days in August – but Cole realised that an employee parking lot might be briefly expendable.

He picks up the keys to the terminal this week, and is ready to show it off before the games that begin on July 27 and end Aug. 12. He’s confident that Olympians will be so happy while leaving – after having an as yet undefined but suitably British send-off – that they will go home pondering a switch from coffee to tea.

“This is not just a tent you put athletes through,” he said. “It’s the start and finish line. We are the first and last impression of the country.”

Even with a special terminal, organizers face a monumental task on Aug. 13 – likely to be the busiest day ever in Heathrow history. How will they cope?

First of all, they’ll start collecting bags at the Athletes’ Village the day before. They’ll install 31 check-in desks, and seven security lanes at the temporary athlete’s terminal. And they’ll make sure there are buses to take athletes to their terminal for departure, where they will be greeted with rounds of applause.

Every plane will get a wave off. Nice! Volunteers will help with that part. Cole promises other surprises – but says that if he describes them, they wouldn’t be a surprise.

He says the Games Terminal will be decorated. At the moment though, it looks like a bit like a big white plastic box. It has some artificial turf and a few scanners but otherwise is just plain empty. The air conditioning isn’t turned on yet – a point Cole brings up at least four times, apparently fearful it will be described as hot – but he swears it will be comfortable come the games.

Afterward, the employees regain the parking lot. It’s Heathrow. It will be busy. But it will be back to normal.

And Aug. 13 will be but a dream.

“It’s very unlikely we’ll ever see a day like that again,” Cole said.