According to an Expedia survey, a quarter of Americans would spring for an upgrade to first or business class. (Getty Images/Hero Images)

Imagine this scenario: An American and a Singaporean are flying together on a cross-country trip. An aisle seat upgrade becomes available, for a fee. Which passenger will open her wallet first?

If you picked the Singapore traveler, you know your Passenger Preferences Index. In the recent survey by Expedia and Northstar, a consulting firm, more than 11,000 travelers from 22 countries across Asia Pacific, Europe, and North and South America opined on a range of air travel topics. Among the subjects: for-purchase amenities, checked baggage fees, in-flight diversions and annoying passenger behaviors. Here are some of the findings:

■ On flights shorter than three hours, Americans are less likely than nearly every other nationality to pay extra for amenities. For example, 15 percent of Americans would pay for “a full meal,” compared with 45 percent of Chinese and 26 percent worldwide. However, 13 percent of Americans would spend money on alcohol, a whisker above the 10 percent global average.

As flight times lengthen, Americans start to unpinch their wallets, though travelers from Mexico, India, Thailand and China are most likely to pay for extra comforts on long flights. On trips lasting seven to 12 hours, nearly half of U.S. respondents said they would pay for a full meal, 41 percent would pay for additional leg room and 20 percent would throw down the plastic for alcohol. Only Singaporeans outrank Americans in the category of splurging on an aisle seat. For upgrades, travelers from Mexico are more likely to go after the choice seats in first and business class. Canadians are the least likely, and about a quarter of Americans would spring for the perk.

■ On flights of 10-plus hours, Americans’ main occupations are sleeping (79 percent), reading (63 percent), eating (62 percent) and enjoying the in-flight entertainment center (51 percent). In addition, more than 20 percent would consume alcohol, 13 percent would relax with the aid of prescription medication and 8 percent would meditate.

■ What can’t passengers fly without? For Americans, the top five include water, phone/mobile device, headphones, a meal and publications such as magazines and newspapers. For 14 percent of Australians, alcohol is a priority — a tad higher than the 13 percent of Americans who need their meds.

■ The world has spoken: 70 percent of global travelers will “avoid baggage fees at all costs.” Nearly 60 percent of Americans prefer carry-on luggage so they can skip the wait at the baggage carousel, and nearly half don’t check bags because they fear the Land of the Lost Luggage.

■ Americans really value their child-free quiet zones: Nearly 20 percent would pay for the special section on flights exceeding 12 hours. But passengers from Mexico, Thailand and Taiwan professed an even stronger yen for the no-wailing zones.

■ Annoying seatmates are a universal grievance. The Rear Seat Kicker, Inattentive Parents and the Aromatic Passenger earned the dishonor of “most infuriating co-passengers” on long flights. However, there were some outliers. Norwegians and South Koreans can’t tolerate the Boozer; Indians abhor the Snorer; and the Japanese and Chinese plug their ears against the Audio Insensitive.

■ Comfort is a worldwide fashion trend, with 88 percent of travelers choosing comfy over chic. Thais, Norwegians and Mexicans, however, cared the most about their high-altitude style.

For additional findings, see https://viewfinder.expedia.com.

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