By plane refers to the mode of transportation that involves traveling in an aircraft, such as an airplane or helicopter. This method of travel is characterized by its speed, efficiency, and ability to cover long distances quickly. It is one of the most popular forms of long-distance travel in the United States and around the world.

The preference for air travel is driven by several factors. Firstly, planes can travel at speeds of up to 600 miles per hour (965 kilometers per hour), making them significantly faster than other modes of transportation like trains or cars. This speed is particularly beneficial for business travelers or those with tight schedules who need to reach their destination as quickly as possible.

According to the U.S. Department of Transportation, in 2020, there were approximately 1.1 billion domestic air trips in the United States. This data highlights the widespread use of air travel within the country. Additionally, the convenience of airports, which are often located in or near major cities, makes air travel accessible to a large portion of the population.

Another reason for the popularity of air travel is its ability to connect distant locations. For instance, flights can transport passengers from New York City to Los Angeles in just under four hours, a journey that would take over 40 hours by car. This connectivity is crucial for both personal and business travel, as it allows people to visit family, attend meetings, or explore new places without spending excessive time in transit.

Furthermore, air travel is often more comfortable than other modes of transportation. Airplanes provide amenities such as in-flight entertainment, comfortable seating, and sometimes even Wi-Fi, making the journey more enjoyable. This aspect is particularly important for long-haul flights, where passengers may spend several hours in the air.

In conclusion, "by plane" refers to the mode of transportation that involves traveling in an aircraft, offering speed, efficiency, and convenience. The popularity of air travel in the United States is evident through the high number of domestic air trips and the ability of planes to connect distant locations quickly and comfortably.