NARITA, Japan March 16, 2011 -- Panicked passengers hoping to flee Japan waited for hours at the country's largest international airport today as concerns about radioactive fallout heightened.

The international and domestic terminals at Narita International Airport were crammed with passengers leaving the capital after a small spike in radiation levels were detected in Tokyo following a reactor fire that has raged for two days at a troubled nuclear plant 150 miles north of the city.

Four of the plant's six reactors were damaged in last Friday's earthquake. People living in a 30 kilometer radius of the plant were evacuated, but those further away are no less nervous.

Germany's Lufthansa airline became the first major carrier to cancel flights to Narita International Airport, which services Tokyo, and will reroute all flights through Nagoya and Osaka, some 300 miles south of the capitol. Dutch carrier KLM followed.

The U.S. Federal Aviation Administration said, "There is no credible information available at this point indicating" a need to avoid Narita airport.

The FAA suggested that could change if "the situation at Fukushima worsens and we see credible indications that radiological hazards to civil aviation exist."

While the United States and Britain told their citizens to avoid non-essential travel to Tokyo, France told its citizens to evacuate the city, a markedly different instruction than from the government urging residents to remain calm.

Korean Airlines arranged special charter flights out of Narita to take Koreans out. The company offered discounted one-way tickets. Priority goes to Koreans living in Japan who are likely to be affected by the explosion.

China organized a mass evacuation of the thousands of Chinese who work in factories in the Fukushima area, planning to bus them to the airport and bringing in extra flights to take them home.

"It was a spur of the moment decision," said Adam Lobel, an American expatriate who has lived in Japan for 11 years but decided to fly to New York today.

"It is a heart-wrenching decision, but the situation does not appear good," he said while standing in line with his wife to check in at Narita airport.

Lobel said he would "assess the situation" and planned to return next week if things had become more settled.

Lobel said he arrived at the airport five hours early anticipating long lines.

Many of the city's international schools closed for two weeks in the wake of the earthquake and many of the people leaving from Narita were families with young children.

Julia Chang frantically worked the phones to find a flight out of Japan to either South Korea or China for her 11-year-old daughter, who is a student at one of the city's international schools.

"I just want to make sure my daughter is safe. Everything's so confusing and we don't know who to believe. I'm not taking chances with my girl," Chang said.

Chang was able to book a flight only for her daughter to leave on Friday to Seoul, South Korea, where she can stay with her grandmother.

Those who can't leave the country or are keeping their options open are moving further south to Osaka.

Emperor Akihito, the country's revered 77-year-old monarch did little to reassure the country in a rare public address, saying: "With the help of those involved I hope things will not get worse."

Tokyo Exodus in Face of Radiation

Though Tokyo was not significantly impacted by the earthquake, five days later shelves in shops and supermarkets were empty of food, as nervous residents stockpiled.

Just outside the Fukushima plant, radiation levels briefly reached 10 miliseiverts per hour, about the equivalent of a CT scan for one hour. Levels fell through the day but remained high, said government spokesman Chief Cabinet Secretary Yukio Edano.

In nearby Ibaraki prefecture, officials reported radiation levels at 300 times the normal amount. While those levels could be dangerous over long periods of time, they are not, fatal, experts said.

ABC News' Joohee Cho and Matt Hosford contributed to this report