Immigrants deported from the United States arrive on an ICE deportation flight on February 9, 2017 in Guatemala City, Guatemala.
CNN  — 

It’s the first flight for many people who file onto these planes. But it’s not a happy occasion.

Guards patrol the aisles. The passengers are handcuffed. And all of them have one-way tickets.

Planes chartered by ICE Air Operations, the division of Immigration and Customs Enforcement that coordinates the transportation and deportation of detained immigrants, fly more than 100,000 people back to their home countries every year.

And with President Trump vowing to increase deportations, it’s possible that number will climb.

Who flies on ICE Air? Where do deportation flights go? And how much do they cost?

Here’s a snapshot:

Planes chartered by ICE Air have deported hundreds of thousands of people.

In 2016, more than 110,000 people were removed from the United States on flights chartered by ICE Air.

ICE Air Operations also deported more than 6,100 people on commercial flights that year.

The aircraft also fly domestically, transporting immigration detainees.

Sometimes, ICE Air flies immigrants to detention centers across the United States. Other times, it transports them to cities near the border, where they might be bused across and deported.

Domestic flight destinations include a number of major US cities, including Seattle, San Francisco, Las Vegas, New Orleans, Denver, Salt Lake City, Miami and Chicago. Flights also regularly land at airports in small cities that are ICE Air hubs or near immigration detention centers.

While its elaborate route map looks like a page from a commercial carrier’s in-flight magazine, there’s at least one way ICE Air’s flights are different from many domestic flights.

Passengers do get a free meal onboard.

Most international ICE Air flights travel to Central America.

ICE deported people to 185 countries in 2016. A snapshot of ICE Air’s top deportation destinations paints a picture of recent immigration trends. The majority of immigrants who were repatriated on charter flights headed to Central America.

Nearly a third of ICE’s 240,255 deportees in fiscal year 2016 were from three countries in that region – Guatemala, Honduras and El Salvador – where experts say growing violence and economic problems have helped fuel a wave of immigration.

ICE Air is only one of the ways the United States deports people.

Take Mexico, for example, the country where the US deported the largest number of people in 2016.

Of the people ICE deported to Mexico in 2016, just over 10% left on flights coordinated by ICE Air. The other removals occurred via bus or on foot, according to Immigration and Customs Enforcement.

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ICE Air charters a range of different planes.

The agency’s five charter contracts provide up to 10 aircraft for routine flights, each capable of carrying a maximum of 135 detainees, according to ICE.

For missions deemed high-risk because they involve the transportation of serious criminals, including violent offenders, ICE Air sometimes uses small jets.

It’s not cheap.

Transporting deportees to their home countries cost an average of $1,978 per person in 2016, according to ICE.

A chartered flight costs about $7,785 per flight hour, ICE says. That covers the cost of not only the aircraft and fuel, but also a pilot, flight crew, security personnel and a nurse onboard.

A 2015 report from the Department of Homeland Security’s Office of Inspector General criticized the agency for flying detainees on flights that weren’t full, concluding that ICE Air could have saved more than $41 million by optimizing flight capacity.

In its response to the assessment, ICE said looking at the number of empty seats on planes wasn’t the correct way to measure the efficiency of ICE Air.

“Delaying the removal of individuals in order to fill empty seats incurs costs that may exceed the cost of empty seats,” ICE said at the time, noting that it cost about $122 per day to house a detainee in immigrant detention.

“It makes no fiscal sense to delay a large group of detainees to fill a small number of vacant seats.”

The number of ICE Air flights could grow.

About 47% more people were deported on ICE Air flights in February 2017 compared to the same month the previous year. But we’re not seeing a Trump bump – yet.

In fact, more people were deported on ICE Air in the last full month of Obama’s presidency than in Trump’s first full month in power. And so far, Trump appears to be deporting fewer people than his predecessor.

Still, it’s possible we’ll see the numbers grow in the future given the Trump administration’s vow to deport more people.

In its 2018 budget proposal, the White House asked for an additional $1.5 billion to expand efforts to detain, transport and deport undocumented immigrants.

CNN’s Leyla Santiago, Tal Kopan and Octavio Blanco contributed to this report.