Long layovers are a pain for many travellers who dread killing time in airport lounges. But with a bit of planning, a long layover can be an extra adventure on a trip.
Though it varies by airport, a layover of six hours or more may allow travellers to leave the lounges and explore the surroundings and even a nearby city before hopping back on the plane to your final destination.
This can be accomplished independently or by a transit tour, which a number of airports and tour companies now offer.
Changi Airport introduced its Free Singapore Tour in 1987 as a way to entertain passengers with long layovers and to encourage visits to the city.
There are two tour itineraries, a Heritage Tour of key historic sites such as Chinatown and the colonial district, and a City Lights Tour, which takes tourists to sites such as Marina Bay Waterfront Promenade, Gardens by the Bay and the Singapore Flyer at night.
A Changi Airport Group spokesman says 50,000 people take the tours every year. "Thirty per cent of passenger traffic at Changi Airport are transferring passengers who, under normal circumstances, would not even step out of Changi.
"With the Free Singapore Tour, we hope that transit passengers who go on it will be encouraged to return to Singapore for a longer stay soon."
Airports around the world also offer tours and transport to destination highlights, from the beaches of California to the temples of Seoul and the forests of Frankfurt. It is like a vacation within a vacation while in transit.
A long layover may even lower the overall cost of a trip as flights with a long transit are often cheaper than direct flights and allow travellers to see a new city without having to pay for an extra plane ticket or hotel room.
Ms Alicia Seah, a spokesman for Dynasty Travel, says that by opting for a stopover, travellers will get to explore a city which they will pass through anyway. "It is like two plane tickets for the price of one," she adds.
A Delta Airlines ticket from Singapore to New York costing $1,635 return involves a 10-hour layover, which can be used to see Hollywood Boulevard and the Hollywood Walk of Fame in Los Angeles.
A KLM flight from Singapore to Paris, priced at $1,391 for a return trip, has an eight- to 16-hour layover in Amsterdam. That is enough to visit the city's canals and Van Gogh Museum.
You may need only a three- to four-hour layover to enjoy sights in some cities. At Seoul's Incheon, the airport offers a free one-hour tour to a nearby temple. From Frankfurt Airport, transit passengers can catch a public bus and, in 15 minutes, walk through an old oak forest and a children's playground.
There are constraints, however. Transit tours are more likely to find favour with younger and more independent travellers, says Ms Seah. "Families with young children, older folks or business travellers will opt for direct flights in view of shorter flight time and ease," she notes.
Because of long immigration, Customs and security queues in busy or intensely high-security airports such as Los Angeles International Airport or London Heathrow Airport, one is not advised to leave with a layover shorter than seven hours.
Transit passengers must also keep visa requirements, transport times and luggage restrictions in mind when planning a transit trip.
While it is best to check in one's bags all the way to the final destination, when flying via multiple airlines, travellers may have to stow baggage at a luggage storage station at the airport or take it with them.
There are websites such as Layover Guide (www.layoverguide.com) and Smart Layover (smartlayover.com) which help travellers design their transit trips. TripAdvisor also has layover information and advice for different cities.
Here are eight transit destinations to get started.