LOS ANGELES — When Steven Udvar-Hazy was a teenager in New York City, he would often head after school to Idlewild Airport, as Kennedy International was known then, to watch planes take off and land.

Airplanes symbolized freedom to the young Mr. Hazy, whose family moved from Hungary when he was 12. For hours, he would spot different aircraft and pore over timetables to figure out where they were coming from, or headed to.

Today, if anyone were to watch planes taking off at Kennedy — or at most airports around the world — they probably would be looking at planes owned by Mr. Hazy, a billionaire three times over and one of the most powerful players in commercial aviation.

As founder and chief executive of the Los Angeles-based International Lease Finance Corporation, Mr. Hazy has a fleet of 824 Boeings and Airbuses, with 254 more on order, that dwarfs any airline’s in the world. He owns more planes than the industry leader, American Airlines, which has 679, and more than the combined holdings of Air France (265), Lufthansa (245) and British Airways (239).