Corruption, chaos, crowds, confusion and lack of cleanliness were all factors that earned Nigeria's Port Harcourt International Airport the current title of world's worst airport. "Five Cs an airport definitely doesn't want to be associated with," says Donna McSherry, founder of Sleeping in Airports, which has held the annual survey since 1996.

Throw into the mix unfriendly staff, a lack of seating, broken air conditioning, a tent serving as the arrival hall, almost non-existent amenities and decrepit buildings, and it is little wonder it won the crown. "It ticks every box when it comes to what an airport shouldn't do," says Seng Hun, who has worked in the travel industry in Southeast Asia for 15 years. "It's important airports get it right because they are generally people's first and last impressions of a country; airports can make or break a holiday."

As world wanderlust has grown dramatically during the last two decades, some airports have led the way in providing passengers with top class facilities to keep them entertained. However, many have failed to keep up, leaving travellers frustrated before they have even boarded the plane.

"Airports contribute strongly to the vibrancy of local communities, and in addition to ensuring travellers are safe and secure, a focus on customer service is vital if this contribution is to be maintained," says Angela Gittens, director general of ACI (Airports Council International) World.

Common Complaints

"In general, the worst airports are those that don't have many amenities for travellers, don't offer complimentary Wi-fi and don't keep the restrooms clean," says Harriet Baskas, a frequent flier and founder of StuckAtTheAirport.com.

Ho Chi Minh City's Tan Son Nhat International Airport, in Vietnam, falls short in many of these areas, according to Jack Bartholomew, Khiri Travel's regional director for Indochina. "It's a truly shocking airport," he says. "There's nothing to do there whatsoever except drink." It clinched the eighth spot in Sleeping in Airports' survey of the world's worst airports, and fourth in Asia; allegations of corruption, problematic paperwork, unhelpful staff, poor Wi-fi, dirty toilets and limited amenities were also cited by voters.

Despite being China's second busiest airport and 16th busiest in the world, Guangzhou Baiyun International Airport secured sixth place on the worst airports in Asia list. "I have wasted so many hours of my life in that airport," says Seng. "There's no Wi-fi unless you have a Chinese mobile number, the bare minimum of facilities, the staff are really unhelpful, it's difficult to co-ordinate, and smells like an ashtray from all the smoking rooms."

Sleeping in Airports placed Nepal's Kathmandu Tribhuvan International Airport at the top of their list of Asia's worst airports, with the appalling bathrooms being a top reason. Tashkent International Airport in Uzbekistan came in second, being referred to as "one of Dante's infernos of hell" by a voter, with queues, queues and more queues being the main gripe. Afghanistan's Kabul Hamid Karzai International Airport's lack of facilities and overall hygiene saw it take third place.

While passengers often expect to spend longer in the airports of developing countries, higher standards are expected from major connecting international airports.

Although it welcomed a record high of 73.4 million passengers in 2014, London's Heathrow fails to hit the mark for Ben Schlappig, travel consultant and founder of onemileatatime.com. Having notched up almost five million miles of flight time in his life, he says the airport is poorly designed, making transiting a "real pain". "It's amazing how far apart some of the terminals are, and how inefficient transport between terminals is," he adds. "This is the airport where I plan the longest connection times."

For him, the single most important factor in a good airport is ease of use. "It's all about how easily you can get from check-in to the gate, and also how easily you can connect between flights," he says. Although he labels New York's La Guardia airport as "hideous" -- U.S. Vice-President Joe Biden compared it to a "third world country" in 2014 -- Schlappig rates it for its ease to get from check-in to the gates and connect between flights.

American Airports

As one of the world's most developed nations, America's airports fall way short of the mark. Online trip calculator Travelmath recently released its 2015 Airport Rankings for the country. Newark Liberty International sat at the bottom of the 322 airports, with 26.9 percent of flights delayed, by an average of 14.1 minutes, followed by La Guardia, where 29.6 percent of flights were delayed, by an average of 14 minutes.

Newark and La Guardia are "probably the most unpleasant airport experiences I have experienced", according to McSherry, who was stuck at both during snowstorms. "They're already cold and uncomfortable when there aren't delays, so adding more crowds and chaos only makes the experience worse," she says. At Newark she paid for a hotel for the first time rather than stay overnight in the airport.

Connecting travellers face lengthy queues in many American airports, with overseas passengers, even if in-transit to a third country, having to claim and recheck luggage, then clear customs and immigration. Then they go to the departure concourse, which is sometimes in a different terminal, and reclear the TSA security checkpoint. "At some terminals, during peak travel times, this process can take two hours or more," says Patrick Smith, a pilot, the author of Cockpit Confidential and askthepilot.com founder.

Reports of the larger U.S. airports being dirty, passenger unfriendly and lacking public transport to the city were also noted. "They're also startlingly noisy," says Smith. "Americans have a strange fixation with public address announcements, and at airports they blare constantly. Babies are crying, CNN news monitors are blaring at every gate, and waves of public address announcements -- most of them pointless and half of them unintelligible -- wash over one another. It makes an already stressful experience that much more so."

High Fliers

Sitting in stark contrast to the boredom, queues, chaos, corruption and uncleanliness of some of the worst airports, the high life awaits in some of the best. Singapore's Changi walked away with the crown in Skytrax Top 100 Airports 2015, followed by Seoul Incheon International, with Hong Kong International Airport ranked fourth. Changi also secured the top spot in Sleeping in Airports' Best Airport survey - a title it has held for nearly two decades.

Hong Kong Airport's efforts to become more sustainable were also recognised at the 2015 World Responsible Tourism Awards, where it was ranked second in the world for Best Innovation for Carbon Reduction, marking the first time an organisation based in Hong Kong has been recognised in these awards.

"Singapore Changi Airport is probably my favourite," says Schlappig. "It's extremely well designed for connections, has incredible shopping, and features great amenities, even for those without lounge access." It also boasts a fish spa, sauna, butterfly garden, a free cinema, multi-storey slide, gym, and free city tour.

Incheon gets Smith's vote for world's most flier-friendly airport. "It's quiet, immaculately clean, easy to navigate, and packed with free amenities," he says. Bangkok's Suvarnabhumi Airport comes in a close second. "Its central terminal is the most visually spectacular airport building I have ever seen. At night, approaching by highway from downtown Bangkok, it looms out of the misty darkness like a goliath space station."

As airports such as these set the standards, and with the potential returns that investing in a decent airport can generate, renovations are reported to be taking place at a rapid rate, which will raise the bar for international travel. "Airports are no longer simply places where planes land and take off," says Gittens. "They're sophisticated businesses that often compete with each other to be the gateways to towns, cities, regions and sometimes entire continents."