Air travel

Air travel is a form of travel in vehicles such as helicopters, hot air balloons, blimps, gliders, hang glider, parachuting, airplanes, jet aircraft, or anything else that can sustain flight.[1] Use of air travel has greatly increased in recent decades – worldwide it doubled between the mid-1980s and the year 2000.[2]

See also: Aviation and Civil aviation
For the airline, see Air Travel (airline).
An S7 Airlines Boeing 767-300ER landing
A Eurocopter AS350B helicopter in flight

Domestic and international flights

Air travel can be separated into two general classifications: national/domestic and international flights. Flights from one point to another within the same country are called domestic flights. Flights from a point in one country to a point within a different country are known as international flights. Travelers can use domestic or international flights in either private or public travel.

Air travel

Travel class on an airplane is usually split into a two, three or four class model service. U.S. domestic flights usually have two classes: economy class and a domestic first class partitioned into cabins. International flights may have up to four classes: economy class; premium economy; business class or club class; and first class.

Most air travel starts and ends at a commercial airport. The typical procedure is check-in; border control; airport security baggage and passenger check before entering the gate; boarding; flying; and pick-up of luggage and – limited to international flights – another border control at the host country's border.

For longer journeys, air travel may consist of several flights with a layover in between. The number of layovers often depends on the number of hub airports the journey is routed through.

Airlines rely either on the point-to-point model or the spoke-and-hub model to operate flights in between airports. The point-to-point model, often used by low-cost carriers such as Southwest,[3] relies on scheduling flights directly between destination airports. The spoke-and-hub model, used by carriers such as American[4] and Delta,[5] relies on scheduling flights to and from hub airports. The hub-and-spoke model allows airlines to connect more destinations and provide more frequent routes, while the point-to-point system allows airlines to avoid layovers and have more cost effective operations.[6]

Environmental effects
Main article: Environmental impact of aviation

Modern aircraft consume less fuel per person and mile travelled than cars when fully booked.[7] This argument in favor of air travel is counterweighted by two facts:

  1. The distances travelled are often significantly larger and will not replace car travel but instead add to it, and
  2. Not every flight is booked out.

Instead, the scheduled flights are predominant, resulting in a far worse fuel efficiency.[8][9][10] According to the ATAG, flights produced 781 million tonnes (769 million long tons) of the greenhouse gas CO2 in 2015 globally, as compared to an estimated total of 36 billion tonnes (35 billion long tons) anthropogenic CO2.[11] Carbon offset is often proposed as solution to mitigate the CO2 emissions of flying. There are many NGO's that offer to compensate CO2 emissions by advancing clean renewable energy, reducing energy consumption and capturing already released carbon in trees or other plants.[12] However, carbon offsetting is a very controversial topic as it only tries to mitigate what has already been emitted.[13]

Health effects
Main article: Health hazards of air travel

Deep vein thrombosis (DVT) is the third-most common vascular disease, next to stroke and heart attack. It is estimated that DVT affects one in 5,000 travellers on long flights.[14][15] Risk increases with exposure to more flights within a short time frame and with increasing duration of flights.[15]

During flight, the aircraft cabin pressure is usually maintained at the equivalent of 6,000–8,000 ft (1,800–2,400 m) above sea level. Most healthy travelers will not notice any effects. However, for travelers with cardiopulmonary diseases (especially those who normally require supplemental oxygen), cerebrovascular disease, anemia, or sickle cell disease, conditions in an aircraft can exacerbate underlying medical conditions. Aircraft cabin air is typically dry, usually 10%–20% humidity, which can cause dryness of the mucous membranes of the eyes and airways.[16]

gollark: Divide the difference in Y by the difference in X, yes.
gollark: Take two of the points, subtract one's Y coordinate from the other one's Y coordinate, and do the same for the X coordinates, and divide the difference in Y coords by the difference in X coords.
gollark: <@379441093558927391> I'm assuming that what you want to do is find the equation of the straight line going through those points. So to do that you need the gradient.
gollark: <@379441093558927391>
gollark: Once you have the gradient you just need to work out the y intercept, so put that into the straight line equation (y = mx + c), substitute in the x and y from one of the points, solve for c (y intercept), and you're done.

See also

References
  1. "Aviation." Encyclopædia Britannica. Accessed June 2011.
  2. "Archived copy" (PDF). Archived from the original (PDF) on 2018-07-08. Retrieved 2013-07-31.CS1 maint: archived copy as title (link)
  3. Andrew Cournoyer (February 13, 2018). "Is Southwest's Low-Cost Strategy Good For The Long Run?". Seeking Alpha.
  4. Bart Jansen (July 26, 2018). "American touts new routes, expansion plans for Dallas and Charlotte". USA Today.
  5. "Delta First in the Air". Delta Museum.
  6. Gerald N. Cook and Jeremy Goodwin (Winter 2018). "Airline Networks: A Comparison of Hub-and Spoke and Point-to-Point Systems". Embry-Riddle Aeronautical University.
  7. Alastair Bland (September 26, 2012). "How Bad Is Air Travel for the Environment?". smithsonian.com. A large passenger jet may consume five gallons of fuel per mile traveled. Is it possible, then, that planes are more efficient than cars?
  8. Megan McArdle (Aug 12, 2013). "Air Travel Is Worse Than a Hummer With Wings". Almost eight times as many passenger miles are traveled by car as by plane, but passenger car travel only accounts for 3 to 4 times as much greenhouse gas emission.
  9. Duncan Clark (2010). "The surprisingly complex truth about planes and climate change". Guardian. if we focus just on the impact over the next five years, then planes currently account for more global warming than all the cars on the world's roads – a stark reversal of the usual comparison. Per passenger mile, things are even more marked: flying turns out to be on average 50 times worse than driving in terms of a five-year warming impact.
  10. Borken-Kleefeld, Jens; Berntsen, Terje; Fuglestvedt, Jan (2010). "Specific Climate Impact of Passenger and Freight Transport" (PDF). Environ. Sci. Technol. 44 (15): 5700–5706. doi:10.1021/es9039693.
  11. "Facts & figures".
  12. United Nations Carbon Offset Platform (n.d.). What is offsetting?.
  13. The Telegraph (2007). Pros and cons of carbon offsetting.
  14. Marchitelli, Rosa (30 May 2016). "Air Canada passenger suffers 'horrible pain' after being stuck in cramped seat". CBC. Retrieved 30 May 2016.
  15. Kuipers, S; Cannegieter, SC; Middeldorp, S; Robyn, L; Büller, HR; Rosendaal, FR (2007). "The absolute risk of venous thrombosis after air travel: a cohort study of 8,755 employees of international organisations". PLoS Med. 4 (9): e290. doi:10.1371/journal.pmed.0040290. PMC 1989755. PMID 17896862.
  16. "Air Travel - Chapter 6 - 2018 Yellow Book | Travelers' Health | CDC".
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