Spotting a cargo aircraft often prompts a double-take: hang on, that plane has no windows.
We're so used to seeing passenger jets milling about the tarmac at airports that when a sleek, cylindrical postal airliner rolls past, it comes as a bit of a shock.
But those windowless planes are the key to a multi-billion pound industry. An industry at which FedEx Express sits at the forefront, shifting some 15.7 billion tonne-kilometres of freight a year, more than double some of its rivals.
Behind such a massive global operation are more fantastic numbers. FedEx's airline cargo division boasts a huge fleet of 691 aircraft, twice as many as Ryanair, Europe's largest airline, and nearly six times as many as Qantas.
With a "superhub" at Memphis International, the company flies to more than 375 destinations (Turkish Airlines, which flies to more countries than any other passenger airline, only serves 302), transporting around 5.5 million packages every day. That's as if the entire population of Finland sent a parcel inside 24 hours.
The cargo behemoth, founded in 1971, uses a number of international hubs in addition to Memphis, with European bases at Paris Charles de Gaulle, Malpensa, Milan, and Cologne Bonn. In the UK, FedEx Express is based at Stansted, from where it flies to Memphis six times a week, reaching, it claims, 99 per cent of all US destinations overnight.
So what are its aircraft like?
Just like passenger planes - only there are no seats. Often, the only people on the aircraft are the pilots, and maybe a flight engineer.
FedEx has begun phasing out some of its older aircraft, replacing its Boeing 727s with the more fuel efficient 757s, and swapping out its MD-11s for 777s on its long-range routes, allowing the MD-11s to take over from the DC-10.
Despite its new additions, FedEx's overall fleet has an average age of 22 years, according to AirFleets.net, compared to, say, EasyJet's, which has an average age of six years. The cargo airline has 110 757s, with an average age of 25 years, seven Airbus A310s with an average age of 30 years and 38 McDonnell Douglas DC-10s, with an average of 39.6 years.
Many cargo aircraft are decommissioned passenger jets, stripped and repurposed for carrying freight, with some given strengthened flight deck doors so that the crew is not crushed by its cargo in the event of a crash.
FedEx's largest aircraft is the 777, capable of carrying 102 metric tonnes. The carrier says these planes run six direct routes, including Memphis to Dubai to Delhi to Paris and back to Memphis. Likewise, if you have a few parcels going to Shenzhen, Memphis, Anchorage, Narita and Incheon, you're in luck.
What's it like flying a cargo plane?
Patrick Smith, pilot and author of Cockpit Confidential, says that cargo airlines offer some of the best rates of pay in the industry - and are better protected from dips in the economy, meaning more job security for staff. However, it comes with its own bleary-eyed stress.
"Pilots can reduce the risk of [being laid off] by embracing the lucrative but less-than glamorous realm of cargo flying," he writes.
"If the greasy glare of warehouse lights at 4am doesn't cramp your style, you can hunker down one of the more recession-resistant seniority lists at FedEx, UPS, Atlas Air etc.
"You won't be signing autographs for little kids, and your circadian might graph out a little funny, but lay-offs aren't as common in the freight business."
Is it easy because there are no passengers?
It seems there is no doubt some positives to be taken from there being no chance of having to divert due to an out of control hen party, but flying cargo planes does come with other concerns.
For one, FedEx has to run a pretty tight ship. Its whole business is built on quick, reliable delivery. FedEx says it can reach anywhere in North America the next day, and anywhere in the world in up to four days.
What about the more bizarre cargo aircraft?
Airbus Beluga Photo: Airbus
As well as the 747s and 777s, there are some that were never meant for passengers, whose purpose was always to carry freight.
Like the Airbus Beluga. Only five of the "Super Transporters" have ever been built, but their uses have been myriad, from delivering chemical tanks to carrying an enormous 19th century painting by Eugene Delacroix. In 2004, a Beluga was used to supply relief aid to the Indian Ocean region in the wake of the major tsunami.
Airbus is currently developing the Beluga XL set to replace its older brother by 2020.
Boeing's answer to the Beluga, is the Dreamlifter. Introduced in 2007, the four in service were all converted from 747s bought back by the manufacturer. Boeing Commercial Airplanes president Scott Carson once apologised to 747 designer Joe Sutter, saying he was "sorry for what we did to your plane".
The Telegraph, London