In the first penalty of its kind, the Transportation Department fined American Eagle US$900,000 today for lengthy tarmac delays when thunderstorms swept Chicago's O'Hare International Airport on May 29.

"We put the tarmac rule in place to protect passengers, and we take any violation very seriously," Transportation Secretary Ray LaHood said in announcing the fine. "We will work to ensure that airlines and airports coordinate their resources and plans to avoid keeping passengers delayed on the tarmac."

American Eagle, the only airline with lengthy delays at O'Hare that day, agreed to the settlement it blamed on a slow-moving weather system that resulted in airport congestion. The airline offered customers an apology with vouchers for future travel or frequent-flier miles.

"American Eagle is absolutely committed to the safety of our customers and employees, and regrets the inconvenience these delays caused," said airline President and CEO Dan Garton. "We take our responsibility to comply with all of the department's requirements very seriously and have already put in place processes to avoid such an occurrence in the future."

The department created fines of up to US$27,500 per passenger in April 2010 when travelers are stuck on planes delayed on tarmacs longer than three hours.

Transportation officials credited the threat of fines with dramatically reducing the number of tarmac delays. Airlines, which blame unpredictable weather for the delays, say they're canceling more flights rather than risk fines.

The 20 long tarmac delays in the 12 months after the fines were created reflected an enormous drop from the 693 such delays reported in the year before the fines.

So far this year, American Eagle has had 16 tarmac delays of at least three hours, according to the department. That's twice as many as second-place Delta Air Lines.

O'Hare registered 20 of the 39 the department counted so far this year. On May 29, American Eagle had 15 flights arriving at O'Hare that each had tarmac delays of at least three hours. A total of 608 passengers were aboard the affected flights.

The airline must pay US$650,000 of the fine within 30 days and up to US$250,000 more in refunds, vouchers or frequent-flier miles for the delayed passengers. The fine comes after 23 weather diversions on Oct. 29 from New York-area airports to Bradley International Airport in Hartford, Conn. One JetBlue flight spent 7½ hours on the tarmac. The government is investigating whether fines are warranted in that case, too.