Flights to Las Vegas make the most money selling beverages out of all domestic routes, according to NBC News.

"Alcohol sales on the way to Vegas are higher for sure than on the way back from Vegas," Brett Proud, the CEO of GuestLogix, a Canadian firm that tracks what people buy when they are flying, said.

Six domestic airlines that were tracked for the first six months of the year were found to have made 58 percent of their onboard revenue from selling beverages. Comparatively, 38 percent of revenue came from food sales and four percent came from the sale of comfort items such as headphones and movies.

"I was on a flight to Vegas just last week, there were a lot of people getting it going early," Evan Sears, a frequent flier, told NBC.

Another trend that stood out was the unsurprising fact that the longer the flight, the more people spend.

"On flights with durations of two and a half hours, we're seeing more and more folks open up a tab onboard," Proud said.

The routes in the U.S. that make the most money on drinks include Detroit to Las Vegas, with average drink sales per flight of $179.12, Seattle to Orlando, with sales of $154.08 and Minneapolis to Fort Myers, Florida, with sales of $145.07.

Another interesting fact is that drink sales onboard flights are the highest on Thursdays. According to Proud, this may be because people are heading home from business trips and are more likely to unwind with a drink.

The day after a holiday is the slowest for drink sales.

Passenger comfort items have had sales growth of 19 percent this year, and it's also the area where airlines are seeing the most growth.

The combination of passengers becoming more comfortable buying onboard a flight with a credit card, combined with airlines looking to capitalize on an audience that can't go anywhere will result in even more in-flight sales, according to Proud.