The 'big three' US airlines, namely America, Delta, and United, have some of the largest fleets in the world, with each having hundreds of active aircraft at its disposal. Among these are a wide range of designs, with older examples having spent a considerable amount of time in the air. But which of them are the busiest?

American Airlines

Starting alphabetically with American Airlines, data from ch-aviation.com shows that the Fort Worth-based carrier has 862 active aircraft at its disposal from a total fleet of 911 planes. This represents an impressive proportion of just under 95%. Of these, the single active aircraft that has accrued the most hours is N779AN.

This registration corresponds to a 22.94-year-old Boeing 777-200ER that has flown for American Airlines for its entire career. During this time, it has racked up an impressive 89,819 flight hours (as of February 2022) across 10,958 cycles. This works out at 3,951.78 hours a year across 482 cycles (averaging around 1.32 per day).

Meanwhile, the active American Airlines aircraft with the most cycles under its belt at the time of the last measuring is an Airbus A319-100 registered as N722US. This 22.67-year-old twinjet had flown 35,928 flight cycles as of February 2022, racking up 60,737 hours in the process. This equates to 1,600 a year, or 4.38 per day.

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Delta Air Lines

Meanwhile, American's SkyTeam rival Delta Air Lines presently has 790 active planes at its disposal, accounting for just under 88% of its 899-aircraft fleet. Of these, the most-used jet is almost 10 years older than that of American Airlines. Correspondingly, it has accrued considerably more hours over its 32.09-year career.

Registered as N171DN, this Boeing 767-300ER had amassed 137,377 flight hours across 20,001 cycles as of February 2022. This works out at 4,309.26 hours across 627 cycles (1.72 per day) over an average year. Its average cycle length is six hours and 52 minutes, with a mean daily utilization of 11 hours and 49 minutes.

While American's active aircraft with the most cycles was an Airbus design, Delta's belongs to Boeing. Specifically, N667DN is a 31.2-year-old 757-200 that, as of February 2022, had flown 43,184 flight cycles (amounting to 95,099 cycles) during its career. These were two hours and 12 minutes long on average.

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United Airlines

Third and finally, 696 of United Airlines' 868 aircraft are currently active. However, this figure is set to rise, with the carrier set to reintroduce its Pratt & Whitney-powered Boeing 777s back into service imminently. For now, its most-used aircraft is N643UA, a 31.06-year-old Boeing 767-300ER with 123,126 flight hours under its belt. It has accrued these across 19,204 cycles (623 per year, 1.71 per day).

Meanwhile, the active United Airlines aircraft with the most cycles flown is N414UA, a 28.19-year-old Airbus A320-200. This twinjet joined United in July 1994, and it has since flown 34,815 flight cycles, duly accruing 85,941 hours. With a mean of 1,245 cycles a year, N414UA averages out at around 3.41 cycles per day.

What do you make of these well-used aircraft? Have you ever flown on any of them yourself? Let us know your thoughts and experiences in the comments!