New York - The Federal Aviation Administration said Thursday it had fined American Airlines $1 million and Delta Air Lines Inc $750,000 for violating federal rules prohibiting lengthy tarmac delays at U.S. airports.

Under most circumstances, airlines are prohibited from allowing domestic flights to remain on the tarmac for longer than three hours and international flights for more than four hours without giving passengers an opportunity to deplane.

Of the $1 million assessed to American, $450,000 was credited to the airline for compensating passengers.

Delta was credited with $450,000 for compensating customers and establishing a backup data center and an automated aircraft-parking guidance and jet-bridge positioning system, the FAA said. Read more at Reuters