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. Most passengers must go through these steps when flying with a commercial airline. 

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, relies on scheduling flights directly between destination airports. The spoke-and-hub model, used by carriers such as American and Delta, 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.

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Main article Environmental impact of aviation

Modern aircraft consume less fuel per person and mile traveled than cars when fully booked. However, the distances traveled are often significantly larger and will not replace car travel but instead add to it, and not every flight is booked out.

Instead, the scheduled flights are predominant, resulting in a far worse fuel efficiency. 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.Carbon offset is often proposed as solution to mitigate the CO2 emissions of flying. There are many NGOs that offer to compensate CO2 emissions by advancing clean renewable energy, reducing energy consumption and capturing already released carbon in trees or other plants. However, carbon offsetting is a very controversial topic as it only tries to mitigate what has already been emitted.