If Cupid were to have a home, it would be Miami International Airport.

Flying freight

Worldwide, airlines and air shippers carried about 52 million tons of freight representing $6 trillion worth of goods last year, according to the International Air Transport Association. That was up 1.4% from 2012. The amount of air cargo is expected to climb 17% in the next 5 years.

Even so, competition from cheaper, ocean-going ships has made for rough going for the air cargo business. Rates have been depressed. Air shippers worldwide took in $59 billion in revenue last year, down 12% from 2012.

Source: AP

Before millions of Americans can present their loved ones with a bouquet of Valentine's Day roses, most of the flowers are flown from Colombia and Ecuador to Miami, many in the bellies of passenger planes. There, cargo handlers and customs agents - call them Cupid's helpers - ensure that the beautiful petals stay perfect until they reach their final destination.

In the weeks leading up to Valentine's Day, about 738 million flowers - 85 percent of imported flowers - come through the Florida airport. Los Angeles is a distant second, with 44 million. The roses, carnations, hydrangeas, sunflowers and other varieties are rushed by forklift from planes to chilled warehouses, and then onto refrigerated trucks or other planes and eventually delivered to florists, gas stations and grocery stores across the country.

"We always joke that a passenger gets themselves to the next flight while a bit of cargo does not," says Jim Butler, president of cargo operations at American Airlines.

The biggest problem this Valentine's Day might be the final few miles of the journey. A massive snowstorm that blanketed the East Coast made some suburban roads difficult for local delivery drivers. For U.S. passenger airlines such as American, cargo is a small, but increasingly important part of their business. New jets are built with more freight space and the airlines are adding new nonstop international routes popular with shippers.

There's fresh Alaskan salmon, this season's latest luxury clothing from Milan and plenty of Peruvian asparagus heading to London. Then there are the more unusual items like human corneas. And there are the flowers.

Valentine's Day is a big day for flowers, topped only by Mother's Day, and cargo teams work extra hours ahead of both to ensure on-time deliveries.

"There's a spark in the air while loading these," says Andy Kirschner, director of cargo sales for Delta Air Lines. "You know this is going to loved ones."

Shipping by air costs about 10 times more than by sea, says David G. Ross, a transportation analyst at Stifel. So, plane rides are reserved for trendy high-end fashion items, the hottest electronics or perishables.

"If it's the new product on the block and everybody wants it, then you can ship it by air," Ross says.

The airlines don't break out cargo costs, but the side business is said to be profitable. They already have the jets and are paying the pilots, and they fill planes with enough passengers to cover their expenses. Plus, there's plenty of space next to the passenger luggage in a wide-body jet.

"It's incremental revenue. You're already paying for the airplane to go," says Brandon Fried, executive director of the Airforwarders Association, the trade group for shippers.

Delta considered replacing the Boeing 777s it uses between Los Angeles and Sydney with 747s, which seat 107 extra passengers. But that would have reduced the capacity for the strawberries, asparagus, green onions, lettuce and other perishable items it ships from California to Australia.

The cargo business isn't just about the space in a plane's belly. There needs to also be precision handling on the ground, especially with a product that can spoil. With flowers, as soon as they're cut, a clock starts ticking. And nobody wants to give wilted roses on Valentine's Day.

Heat is the enemy. When a plane touches down in Miami, the flowers are rushed to a nearby warehouse where forklifts carry them into giant coolers set at 35 degrees.

Inside, big vacuums suck the hot air out of flower boxes and bring in the surrounding cold air. In one hour, the core temperature of flowers, vegetables or other perishables drops 46 degrees.

"It's like it cryogenically extends the life," says Nathaniel R. Miller, a supervisor with Perishable Handling Specialists, which operates American's Miami coolers.

Before the flowers can be sent to stores across the country, U.S. Customs and Border Protection must sign off. Agents check tax documentation, ensure that drugs aren't being smuggled and inspect for pests that can ruin crops.

The job has hazards: roses come with plenty of thorns and some officers wear masks to protect against the pollen. Their uniforms include hats and gloves.

"It's like working in a meat locker," says Michael DiBlasi, a Customs agriculture specialist. "We love our job. You have to, to work in a cooler."