Just as much a symbol of the presidency as the White House itself, Air Force One is one of the world’s most recognizable planes. This flying command center is responsible for bringing the Commander-in-Chief wherever they need to go around the globe, during both times of peace and through the uncertainty of war. Here are a few things you might not know about Air Force One.

1. Air Force One isn’t technically the name of a plane.

When someone says "Air Force One," they could be describing a couple of different things. The term is actually a general call sign used for any Air Force aircraft that the president of the United States is currently on. If a president is on a civilian aircraft—such as a personal plane—that plane is known as "Executive One." Now, though, it’s pretty much accepted to also use "Air Force One" as the names of the two Boeing 747-200Bs that the president regularly travels in, even when they're not on it. (We’ll also be referring to these planes as "Air Force One" throughout the article.)

"Air Force Two" is the call sign for any Air Force aircraft carrying the vice president, who is usually found in a Boeing C-32. For security reasons, the vice president and the president never fly on the same plane together.

2. President Dwight D. Eisenhower was the first to use the Air Force One call sign.

Theodore Roosevelt is known as the "first flying president" after he took a ride in a Wright biplane in St. Louis, Missouri, on October 11, 1910, a year and a half after leaving office. Franklin Delano Roosevelt later became the first sitting president to fly in a plane when traveling overseas to a World War II conference.

The term Air Force One wasn’t used until Dwight D. Eisenhower took office. According to a story told in Popular Mechanics, one possible reason behind the call sign came in 1953, when a nearby commercial aircraft was using the same "8610" sign as the president's plane, which could have led to a potentially dangerous mishap. Another consideration was that, as Commander-in-Chief of the military, it was important to not only know where the presidential airplane was, but whether the president was on it. This was especially true as the Cold War ramped up.

Of course, Eisenhower didn’t enjoy the same luxury of the current 747s back in the 1950s. While the Lockheed VC-121 Constellation used at the time had office space and a small communications center, it only held about 16 people and didn’t contain nearly as many amenities as today’s planes.

3. Air Force One has offices, a bedroom, and a medical center on board.

President Bill Clinton aboard Air Force One in November 1997.Cynthia Johnson/Liaison

The list of amenities on the modern Air Force One seems never-ending. This 800,000-pound 747 has 4000 square feet of space distributed between three levels. The plane houses a large office, bedroom, bathroom, and a conference room that serves as an airborne Oval Office. There’s also a medical center/operating room on board in case of an emergency, with a doctor present on every flight. The kitchen is equipped to prepare up to 2000 meals on a flight and can feed up to 100 people at a time.

4. Communication is protected aboard Air Force One.

Full of electronics, televisions, and phones, Air Force One has everything the president needs in case of a crisis. All onboard electronics are protected against electromagnetic pulses and hackers. The plane also contains "advanced secure communications equipment," but the full details of what that entails are not available to the public. However, the White House states that the president would have everything necessary to respond to an attack on the United States while in the air.

5. Air Force One can be refueled in midair.

Air Force One can top off its tank in the middle of a flight when necessary. This gives the plane the impressive ability to stay in the air indefinitely should the need arise. The feat is possible with the help of a fuel plane that flies overhead and refills Air Force One through the aircraft's nose. While useful, the plane has apparently never made use of the capability while a president has been on board.

6. Another presidential plane is known as the "Flying Pentagon."

While the 747s have some impressive security features, there’s another plane out there that's prepared for a much bleaker outcome. In the 1970s, the U.S. military designed and built four Boeing E-4s as a way to protect the president and key government officials during the Cold War in the event of a nuclear attack. It's a worst-case scenario that has earned the plane nicknames like "the Flying Pentagon" and "the Doomsday Plane."

The exact details of its defenses aren’t available to the public, but it's said these planes are outfitted with radiation-proof windows, thermal and nuclear shielding, and countermeasures against direct fire. It's estimated to house 67 satellite dishes in order to communicate with forces all over the globe should the worst occur.

When the president isn't on it, it's usually reserved for trips taken by the secretary of defense. One also always trails Air Force One during overseas trips should a catastrophe occur.

7. You can pack a lot of people inside Air Force One.

While Air Force One is used to transport the president, dozens of other people tag along for the ride. The plane is equipped to carry up to 76 passengers and typically includes the plane's staff, members of the president's staff, security detail, doctors, cooks, and special guests. The president always uses a private entrance and exit, which means guests riding on Air Force One might never even see the POTUS in person. Journalists are sometimes invited to ride along to press events, although news organizations have to reimburse the government for the cost.

8. Air Force One is deceptively fast.

Even with its larger-than-average size and weight, Air Force One is able to fly at a top speed of about 600 mph. That’s about on par with Boeing’s standard 747, which can hit 570 mph. Apparently, that’s not fast enough for some, as there have been talks of building a supersonic jet for the president as well.

9. Air Force One never parks at a terminal.

You’ll never see Air Force One at an airport terminal. This is partly due to security reasons, but also because the plane needs to be able to take off at a moment’s notice. It takes a long time to taxi in and out of airport hubs and could delay the president in an emergency. (This explains why you always see the president walking down a staircase in the open air after they land.) When a plane isn’t being used, it is parked at Joint Base Andrews, a military facility just outside of Washington, D.C.

10. It costs a fortune to fly Air Force One.

The president's office on Air Force One from September 1990.Consolidated News Pictures/Getty Images

Every feature we’ve mentioned so far comes with a hefty price tag. The exact number will vary depending on a number of factors, but a Freedom of Information Act [PDF] request revealed that it cost over $200,000 an hour to operate Air Force One during one of President Barack Obama's trips from October 2014. This included flight consumables, maintenance, and fuel, which can get pricey considering the plane has a 53,611-gallon capacity. That number actually increases when you consider the cost of the presidential limo or helicopter trip after landing Air Force One.

11. The current Air Force One planes will be replaced soon.

The two planes currently known as Air Force One were first used when George H. W. Bush was in office back in the 1990s and are on track to be replaced sometime in the next few years. The entire project is estimated to cost over $5 billion and will include two new Boeing 747-8 airliners that will become VC-25Bs (that's the military designation) after extensive modifications. Most of the details are being kept secret and the planes aren’t slated for use until 2024. Even with the hefty price tag, the new planes lack some key features of the current aircraft, including the ability to refuel in the air. They will, however, be able to travel much further in a single flight than their predecessors.