It depends on the aircraft, but in general the answer is that there are no regulatory age limitations, and indeed we have many aircraft flying that are 50+ years old.

There is no "hard" legal maximum age for an airplane in terms of years; instead, an aircraft's life is measured in flight cycles (one takeoff and landing) and flight hours. Most commercial jets are designed for a service life of about 25 to 30 years, or roughly 60,000 to 100,000 flight cycles. In 2026, many "classic" aircraft from the 1990s are still flying safely because they undergo rigorous, mandatory maintenance "D-Checks" every 6 to 10 years, where the entire plane is essentially taken apart and inspected for metal fatigue and corrosion. However, once a plane reaches a certain age, the cost of these deep maintenance checks often exceeds the value of the aircraft, leading airlines to retire them for more fuel-efficient models. While a well-maintained 40-year-old plane is technically safe to fly, the economic "retirement age" is typically much lower for the world's leading commercial airlines.