This article was reported by Eric Lipton, Nicola Clark and Andrew W. Lehren and was written by Mr. Lipton.

WASHINGTON  The king of Saudi Arabia wanted the United States to outfit his personal jet with the same high-tech devices as Air Force One. The president of Turkey wanted the Obama administration to let a Turkish astronaut sit in on a NASA space flight. And in Bangladesh, the prime minister pressed the State Department to re-establish landing rights at Kennedy International Airport in New York.

Each of these government leaders had one thing in common: they were trying to decide whether to buy billions of dollars’ worth of commercial jets from Boeing or its European competitor, Airbus. And United States diplomats were acting like marketing agents, offering deals to heads of state and airline executives whose decisions could be influenced by price, performance and, as with all finicky customers with plenty to spend, perks.

This is the high-stakes, international bazaar for large commercial jets, where tens of billions of dollars are on the line, along with hundreds of thousands of high-paying jobs. At its heart, it is a wrestling match fought daily by executives at two giant companies, Boeing and Airbus, in which each controls about half of the global market for such planes.