Aline Klingberg has experienced the good and the bad of Atlanta's new international airport terminal.

Hartsfield-Jackson International Airport's international terminal opened May 16, creating a separate entrance to the airport off I-75 for international travelers. As part of the first wave of travelers to use the new facility, Klingberg and her father flew in on May 17 and ran into some of the operational hiccups in the terminal's early days.

Then, after their road trip through the South, she and her father returned to the terminal Monday for their flight back to Germany and found the process to be a breeze.

Klingberg's night-and-day experience may reflect the kinks of the first days of the terminal's operations and the airport's efforts to fix some of the early problems of heavy crowds, long lines and extensive waits for shuttles, but also the mercurial nature of the international terminal.

The new terminal splits off travelers bound for foreign lands from the steady grind of domestic travelers. For the international terminal, that means volatile ups and downs of passenger traffic. One hour the terminal is mostly empty, and the next it's flooded with people, then soon after it's empty again. Some areas may seem deserted while others are filled with throngs of people.

Klingberg's first encounter with the terminal was amid a logjam. After a long wait at Customs and Border Protection, she and her father went out to the curbside to take a shuttle to the rental car center and found a chaotic crowd.

A number of airport-run shuttles pick up passengers from the new terminal's curbside -- including shuttles to the airport's park-and-ride lot, the domestic terminal and the rental car center -- in addition to private shuttles to off-airport park-and-ride lots and other locations.

"It wasn't clear which [shuttle] we had to take," Klingberg said. With so many impatient travelers, whenever a shuttle came, "everyone rushed to it. Then people in the front of the line suddenly were in the back." The shuttles carry 14 passengers each, and Klingberg said there were close to 100 people waiting. She said they ended up waiting in line for some 45 minutes, and including the wait the drive from the terminal it took close to an hour to get to the rental car center.

But 11 days later for their trip back home, the shuttle ride from the rental car center back to the terminal "worked very well," Klingberg said. "There were no people waiting. The shuttle was right there."

The Memorial Day weekend marks the start of the busy summer travel season, but the day of the holiday itself tends to be less busy. The problems arose when there were too many people, Klingberg observed.

Concessionaires describe the waves of passenger traffic in the international terminal as a "feast or famine" type of situation. They hope airlines will add international flights to keep a more steady stream of traffic all day long. Of course, a concessionaire's feast can be a traveler's nightmare of crowds and lines.

On Monday, traveler Leandra Swanson was enjoying a calm period in the international terminal.

Compared to Hartsfield-Jackson's domestic terminal, "it's not nearly as crowded," said Swanson, who drove to Hartsfield-Jackson from the Knoxville area for a trip to Nassau in the Bahamas. "This seems more convenient."

Others sought more ease of use.

Roy Henriksen of Norway, who had to take a shuttle from one terminal to the other, said that was "kind of a hassle."

"It'd be nice if I could get back on the [people-mover] train" inside the airport, said Henriksen. He also ended up with few places to pass the time in the hours until the Lufthansa ticket counter opened in the afternoon so he could check in for his flight. The international terminal has only one restaurant outside security, which Henriksen said seemed filled with people when he first stopped by.

Gwyn Oates from Easley, S.C. said she was a little concerned about being able to find the new terminal, but discovered the highway signs easily guided her way. She said one confusing thing for travelers will likely be the fact that passengers traveling internationally but connecting in a U.S. city are supposed to check in at the domestic terminal.

"I'm sure there's some kinks that have to be worked out," Oates said. "I imagine it will be confusing for people for a while."