Over the past couple of weeks, the exorbitant cost of presidential travel has made its way into the spotlight.

In fact, President Donald Trump's travel itinerary cost US taxpayers more than $10 million during his first month in office, according to The Washington Post.

Presidential travel is a highly complex logistical operation involving hundreds of people, dozens of vehicles, and a fleet of aircraft.

As a result, it easy to see how the bill can skyrocket very quickly.

So what does this operation entail?

First, there's Air Force One, the call sign given to the Boeing VC-25A when the president is aboard. There are actually two planes that share that designation. The VC-25A is a highly modified version of the Boeing 747-200B airliner. Even though it entered service in 1990 with President George H.W. Bush, the jets — tail numbers 28000 and 29000 — were ordered in the mid-1980s by President Ronald Reagan.

According to Boeing, each aircraft carries a crew of 26 along with roughly 70 passengers including the president, government officials, Secret Service agents, and guests. The 4,000-square-foot space in the VC-25A's cabin allows the aircraft to function as a flying White House with the ability to run a country from 40,000 feet. At the same time, the 747-200B's General Electric CF6-50 series engines were replaced with the more powerful CF6-80 series engines from the newer 747-300.

Other presidential upgrades include:

Midair-refueling capability

Missile-defense systems

Electronic countermeasure defense systems

An operating room

The ability survive the electromagnetic pulse emitted from a nuclear detonation

The communications capabilities to manage a wartime crisis from anywhere in the world

On major trips, both VC-25As make the trip — one with the president aboard and the other acting as backup in case of an emergency.

According to a Freedom of Information Act request filed by Judicial Watch, the VC-25A cost a whopping $206,000 an hour to operate during a 2014 trip to Los Angeles by President Barack Obama. According to the documents, this figure included fuel, flight consumables, and maintenance.

This far exceeds the $20,000 to $25,000 an hour it costs an airline to operate a commercial 747, Airways senior business analyst Vinay Bhaskara told Business Insider in an email.

The VC-25As are operated by the Presidential Airlift Group at Joint Base Andrews in Maryland and are part of the US Air Force's 89th Airlift Wing.

Other travel costs

Then there are the limos. Affectionately known as "The Beast," the presidential limos are heavy-duty armored vehicles built on a General Motors commercial truck platform with a Cadillac body. These monsters feature everything from full-ballistic protection to an on-board cache of blood for the president in case of a medical emergency.

According to Autoweek, each one of Obama's 12 Beast limos cost $1.5 million. Trump will get a new version of the Beast. It's unclear how much the new model will cost.

On trips, these limos travel ahead with the advance team so they are waiting for the president once his plane arrives. This means they have to be transported ahead of time in a fleet of Boeing C-17 Globemaster III cargo planes.

And in instances in which the president is in a hurry, he has the option to bypass the Beast and go with Marine One, the call sign for the presidential helicopter. The helicopters — Sikorsky VH-3D Sea Kings or VH-60Ns or Boeing MV-22s — usually fly in a formation of three. These are operated by the Marine Helicopter Squadron One (HMX-1) in Quantico, Virginia.

So, there you have it. Why is it so expensive for the president to fly? It's the custom jumbo jet, the staff and crew needed to operate the planes, the limos needed to transport the president to and from the plane, the cargo plane needed to transport the limos, and the helicopters in case the president wants to skip the car ride.