Friday morning began with delays at New York's LaGuardia airport. That's not unusual – New York's airports are famous. But this time it was not something as prosaic as a blizzard. It was a crew. Due to the closure of the federal government, the airport did not have enough agents for traffic safety and air traffic controllers. Things slowed to a halt.
Then it all spread – Newark, Philadelphia, even the key point of Atlanta began to relax. And that's scary. Airports are nodes in a global network, and the science that controls the behavior of the network means that a problem spreads when a node has a problem. The international air travel network is on a knife edge. It does not take much to turn off the optimal flow.
Basically, the delay problem is one of the "connected resources". Airplanes land and have to be turned over to perform other flights, and some of the passengers are also entering other flights. If you've ever flown, you know it all, but in practice that means small errors or delays at an airport get bigger as they move along the line, spreading and sometimes amplifying. "The systems that serve these queues are close to capacity," says Hamsa Balakrishnan, an aerospace engineer at MIT who studies the air traffic network. "Both LaGuardia and Newark had wind delays today. With full cast you may have been able to do that, but with a reduction in cast, you have delays that are spreading to other airports because of connectivity. "
Normally you expect the biggest airports In the world ̵
Airlines are trying to take all this into account by limiting the timetable. They calculate the amount of time a particular flight should take – the "scheduled freeze time" – and the time the plane must spend on the ground, the "scheduled turnaround time." But then they have the choice. "They add buffer time to their schedules and ground operations," says Bo Zou, a transportation engineer at the University of Illinois. "There are still delays, and a newly-formed flight delay will spread to the second and third flights. Part of it is absorbed by the buffer, but not by everything. "Build up too small a buffer and the delays continue to spread. Build too big a buffer, and you will not use your fleet efficiently and lose money. "One side is efficiency, the other is robustness," says Zou.
And it is constantly changing, depending on the changing conditions. Outs. This is called a "dynamic complex network". It has to adapt constantly.
Because if not? According to a study, flight delays cost the US economy over $ 30 billion annually. It is not just time loss or airfare; it's what the people on those flights planned when they arrived. "Longer shutdown or even slowing down would probably affect all sorts of unforeseen things," says Luís Bettancourt, network scientist at the University of Chicago. "The reliability of time-critical logistics will diminish, and the lifting nature of some of these cities must be at least temporarily avoided. A sustained slowdown would be devastating for big cities, their influence and their economy.
After the closure has been closed, the government can now bring its TSA agents and air traffic controllers back on station. That will bring some resilience in the airports just in time for a violent snowstorm that will take place next week in the Midwest. However, the overall health of the air transport network will continue to be precarious.
That's why researchers are working to gather more and more data on how everything works (or does not work). If people can not plan these flights in an efficient and robust way, this may be an algorithm. Balakrishnan even co-founded a startup trying to achieve that. "There are so many moving parts that it's hard for a person to find all sorts of solutions," she says. "But that's something we know how we can get computers to do it." Now, if you like to fly in a relentless and incomprehensible network, wait until it is executed by a relentless, incomprehensible robot.