How a control tower works: Managing takeoffs and landings

This story is the second installment of a two-part story about how control towers work. We previously covered how the tower controls aircraft on the ground.

Air traffic control towers loom above airports worldwide. Some of them are spectacularly designed; there's even a coffee table book dedicated to visually stunning examples. One that's unique in appearance (and apparently "controversial" when it was built in 1996) is LAX's sun-bathed control tower, standing some 277 feet above the ground. I recently visited the tower and met with the team there to learn how they work. It was fascinating.

LAX Tower has 36 controllers on its roster, with 22 in training, plus support staff and management. On the day of my visit, there were around eight in the tower at one time.

Not unlike the Seattle Space Needle, the control tower has a so-called octagon "cab" at the top, a pod where the controllers work. The floor is the size of a large living room; I'd estimate around 2,000 square feet. There's a console in the middle for the supervisor, with ground controllers and local controllers lining each side. There are large plastic window shades that are drawn—the outside is very bright but the controllers need to monitor their computer screens. And there is a lot of them.

The tower is a beehive of calm, despite about 144 arrivals and departures per hour, with lots of focused work and not a lot of chatter, except between the controllers and pilots. LAX is one of the busiest airports in the world, with 87.5 million passengers streaming through, and the third-busiest in the world by aircraft movements (takeoff and landings), with more than 700,000 per year. LAX has its daily peak arrivals between 10am and 12:30pm, when transcontinental flights land. After 12:30, you'll see several Airbus A380 long-haul flights arrive from Europe an Asia.

The tower itself is physically located between the sets of parallel runways. Up top, the work is split between ground controllers responsible for the movements of aircraft on the ground and "local controllers" (referred to by pilots as the "tower"). There are two local controllers who manage the inbound and outbound flights. One controller is in charge of parallel runways 25L and 25R. On the opposite side of the cab, a separate controller is in charge of parallel runways 24L and 24R.

"They own the runways," said one controller on my tour.

Most of the operations at LAX are westbound, over the Pacific Ocean, with noise abatement procedures in place from 12:00 AM to 6:00 AM, whereby aircraft will still depart westbound as usual, but land eastbound. This puts takeoffs and landings over the Pacific Ocean, rather than over Los Angeles residential neighborhoods.

On the busier runway 25 side — busier, because there are more gates on that side — a second controller sits next to the controller who is working the runways and airspace; he or she monitors the communications as a backup. The controllers will stay in position for no more than two hours and sometimes less, followed by a half-hour break.

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Communications between the tower and aircraft progress at a measured clip, although the work moves at a fast pace.

The swath of airspace under their control is not huge, by design. The focus of the local controllers are those initial and final moments of flight. For example, shortly after departing, an aircraft will be "handed off" via radio communication to the TRACON, a facility in San Diego that controls portions of the airspace in Southern California. Similar centers exist across the U.S. to control air traffic, with a national facility in Washington, D.C. monitoring all centers and traffic.

This series of handoffs will continue as the aircraft continue onwards to their destination, from center to center.

So, who are the controllers? At LAX and control towers like it, they're seasoned professionals who've done their time at smaller towers. One controller I spoke with started his career in Reno, Nevada, progressing to Seattle - Tacoma and then to LAX Tower, over the course of 10 years. He said most of his colleagues got into the profession because they loved aviation, with several private pilots among the staff. In his case, it's a family business — he has no fewer than three cousins in Northern California who are also air traffic controllers and encouraged him to apply for the job. (If you're intrigued, safety-minded and calm, cool and collected, the FAA is always looking for controllers.)

Their work moves at a fast clip. I listened in as a controller squeezed in a Delta regional jet, a Southwest Airlines Boeing 737 and an AeroMexico Boeing 787, all in quick succession. In the meantime, aircraft landed on the parallel runway, with one coming in and one taking off every minute or so. At LAX, landing aircraft will frequently have to wait for departing aircraft before crossing the runway closest to the terminals.

Here's what I heard.

"AeroMexico 645, line up and wait, Runway 24 left," the tower controller said.

"Line up and wait, Runway 24 left, AeroMexico 645," the pilot operating the radios dutifully read back. This commanded the pilot to taxi forward on to the runway in position to depart, but not actually depart.

Why the wait? An aircraft that had previously landed needed to cross the runway some 9,000 feet down the road.

After that landing aircraft had crossed the runway and it was safe to proceed, the tower controller directed him to depart.

"AeroMexico 645, cleared for takeoff Runway 24 left."

The pilot repeated the instruction back to the tower so that all was clear, throttled up and departed.

Up in the tower, the stream of paper slips and planes kept on coming.

Mike Arnot is the founder of Boarding Pass NYC, a New York-based travel brand, and a marketing consultant to airlines, none of which appear in this story.