Mark Chadwick took a chance on an air courier flight to Tokyo and ended up sipping champagne in first class.

For $175, Chadwick flew from Tokyo to Los Angeles in style -- executive business class style!

"Because I was a courier, I was there really early. So when the flight was overbooked, I got chosen to be bumped up to executive class.

"I wound up sitting on the upper deck and basically had the trip of my life. Talk about first class service," says Chadwick.

Chadwick is one of almost 40,000 people who took courier flights last year. He says if you're an experienced, adventurous traveler, they're a great way to see the world on a limited budget.

"You get a heavily discounted air fare and a chance to see a country you might not otherwise see. It's a great way to travel," says Chadwick, who's traveled to Japan three times as a courier.

It all started for Chadwick about four years ago when he saw an article in the newspaper about courier travel and clipped it out.

Chadwick found he was well suited to air courier travel -- he had a flexible schedule, a small budget, a sense of adventure and a responsible attitude.

"You do have to remember to be professional. It's a business transaction, after all," he says.

Chadwick admits the whole idea of courier travel sounded a little bit like something out of a spy movie at first -- picking up packages at airports and meeting with foreign contacts -- but he says it's a completely respectable business.

"My mother was worried what would happen to me if the company was shipping contraband [illegal] items," says Chadwick, who says this is a common, but incorrect fear.

"It's just a convenient way for them to ship overnight packages. What major company would risk their reputation shipping contraband?"

Despite the many restrictions of courier travel, Chadwick says he'll take it any day over trying to get on a plane with a standby ticket

"Some airlines will give you a discounted flight to fly standby, so they don't fly with empty seats. You can be bumped off these flights, you're not guaranteed a seat and the savings aren't that great. As a courier traveler, you have the same rights as any other passenger," says Chadwick.

While some courier traveler stays can be a long as 30 days, most are in the nine days to two-week range. Chadwick says this is a perfect amount of time.

"It's a perfect amount of time because it's unlikely you'll get bored, nor will you find you don't have enough time to do things."

Even though Chadwick is an experienced traveler, his travel experiences haven't been without their tense moments.

"There was one time when I was a bit worried when no one showed up for a long time to pick up the cargo. Everything worked out fine in the end, but it was a bit tense," says Chadwick, who admits it's not unusual for courier reps to be late in dropping off or picking up the cargo.

Chadwick isn't alone when he says dealing with these unexpected delays and tense moments are all part of what it means to travel as an air courier. The name of the game is flexibility.

Carrie Clement couldn't agree more.

"If you're a very schedule-oriented person and get upset about delays or changes in plans, this might not be the thing for you," says Clement, who has been on four courier trips, all within Western Europe.

While Clement admits Western Europe isn't the best destination for the budget traveler, she says you can't really argue with a return flight from New York to Paris for $250. Flights can be an extremely good deal if the courier company is stuck and needs someone on really short notice.

"I got a call from a company offering me a free ticket if I could leave in a couple of days. Unfortunately, I couldn't at that time, but I'm still hoping to have a chance like that again," says Clement.

With four trips under her belt for the same courier company, Clement says she's on her way to achieving a kind of priority status with the company.

"As you travel more, there's a chance you can get a kind of preferred status, which gets you on a list of contacts who get offered those really cheap, short notice flights. To the courier company, you're a good bet."

While single travelers are best suited to courier travel, Clement says it's not impossible to have a friend join you on a trip. Clement was able to meet up with her husband in London and enjoy a nine-day holiday with him.

"It took a bit of juggling, but we arranged it in advance. I flew out on a Monday and my husband met me the next day." Courier companies are usually willing to arrange sequential flights for people who want to eventually meet up.

So, for less than the cost of one return ticket, Clement and her husband were able to enjoy London together.

"My only problem is getting enough vacation time -- I want to take every trip they offer me!" says Clement.