Over Your Head

Look out the nearest window at the sky. It might be blue, or gray, or dark or bright or full of stars or maybe it's a plethora of colors in sunrise or sunset. Nevertheless, there's a lot going on up there that most people don't think much about, but affects us all. Namely, airplanes.

Lots of airplanes move around all day and night, all across the sky, going about their errands from one place to another. Of course, like all things technical, it's a LOT more complicated than that. There are literally dozens of people involved in even a single flight of a commercial airliner, even if it's just a few hundred miles. Going international, or transcontinental, there may be over 100 people involved, from all walks of life. It's all best illustrated by following a single flight across the country.

The airplane pulls up at the gate, shuts down and offloads passengers and cargo. The aircraft will be changing crews at this stop, so the crew disembarks. Meanwhile, the new captain is receiving his weather briefing and flight plan from a dispatcher. The passengers are checking in with the front desk, checking their bags and receiving seat assignments. They are herded through security checkpoints and their baggage is sorted to arrive at the proper aircraft for loading. Already an entire staff has been involved in even just loading the aircraft. Ground crews at the aircraft load the baggage as well as cargo and mail and fuel the aircraft, communicating and coordinating with the captain and crew, who are already at the aircraft.

The captain is responsible for performing a preflight walk-around (although this unappealing task is generally delegated to a copilot or flight engineer) and once back in the cockpit he or she turns on the radio and communicates with Clearance Delivery to confirm their instrument flight plan. Once they have that clearance, they request a pushback from the ground crew and contact Ground Control and request clearance to taxi. Generally, they start their engines during the pushback. Once they have been pushed to a proper distance from the gate, they begin taxiing towards the runway assigned to them by Clearance Delivery. Quite a bit has happened, considering the passengers only just sat down a few minutes ago and the plane has yet to leave the ground.


Once enroute to the runway, the crew has a lot of work to do. They have already completed multiple checklists by now, and have input their flight plan into the navigation computer or GPS receiver. Now they are completing the before takeoff checklist and running last-minute systems checks, aligning navigational equipment and checking the engines. They get to the runway and contact Tower Control, receiving clearance to take off. They pull onto the runway and increase the engines to takeoff power, accelerating down the runway and taking flight. Very shortly, the tower controller tells the crew to contact a departure controller.

The Tower Controller controls traffic within a few miles and a few thousand vertical feet of the airport. Around many larger airports (the size of Chicago, LA, Minneapolis, Kennedy Int'l) there will be an "Upside-Down Wedding Cake" structure of airspace, basically concentric stratified circles over the airport, going up to 10,000' and out to about 30 miles, although this varies per airport with regards to particular needs and navigational routes nearby.

The Departure Controller vectors the aircraft out of the "Wedding Cake", which is called a Class Bravo Airspace. Once out of the Bravo structure, the Departure controller hands the aircraft off to a Center Controller. Centers are similar to arrival and departure controllers, except they primarily control aircraft in the cruise phase of their flight. A single Center will cover multiple states, and is split into numerous sectors. Each sector is controlled by a single Air Traffic Controller, and they hand the plane off from person to person vectoring it through to it's destination. Across the continent, our flight might contact dozens of sectors. This phase is honestly quite boring, as the aircraft already has a navigation plan and most communication is in regards to altitude changes and handing off from one sector to another.

Once the aircraft gets close to it's destination, within about 70 to 100 miles, the controllers start giving clearances to descend to lower altitudes. Eventually, the aircraft will arrive at the borders of the airspace for it's destination. If this is a very large city, there will be a class bravo. In a medium sized airport, such as Milwaukee, Fargo or Reno, there is probably only a tower. However, there will also be a seperate Departure and Arrival Control, although depending on traffic amounts they may be the same person and frequency. Nevertheless, the aircraft will talk to somebody new. This person will clear the aircraft for an instrument approach, which is a special route designed to line the aircraft up to the runway using only radio navigation, so that planes can land in low clouds and visibility. All airline flights are on instrument flight plans for a variety of reasons, so the use these even in visual conditions.

The aircraft flies the approach and, when close enough to the airport, is handed off to a tower controller who clears the aircraft to land. Once the aircraft lands it taxies clear of the runway and contacts a ground controller, who directs the aircraft to a parking spot or boarding gate, at which point the crew shuts the aircraft down, the passengers deplane and the ground crew set to work unloading the cargo compartment and reloading it with new cargo and baggage and refueling it to repeat the entire process over again.

Those are the people directly responsible with getting the aircraft from point A to point B: flight crew, ground crew at each gate, dispatchers, dozens of air traffic controllers, check-in clerks and baggage sorters, so on and so forth. Beyond that, there are hundreds more people responsible for behind-the-scenes work. Managers, lawyers, FAA and NTSB personnel, aircraft technicians and mechanics, controller supervisors, and the hundreds of people who maintain the radio navigation beacons that help aircraft get across the country and world. Ultimately, the aerospace industry is vast, employing thousands of people and serving upwards of a million pilots and billions of passengers per year.

Something to think about next time you see an airplane above you.

TRH