Delta Air Lines Inc. bumped passengers from oversold flights without informing them of their right to compensation, U.S. regulators said, prompting the second fine against the carrier in four years over that issue.

The penalty was $750,000, the Department of Transportation said in an e-mailed statement. Atlanta-based Delta didn’t seek volunteers to give up their tickets before removing people and didn’t provide required notices to travelers informing them of their rights, the agency said.

“Airline passengers deserve to be treated fairly, especially if they are forced to miss a flight because an airline oversold seats,” U.S. Transportation Secretary Ray LaHood said in the statement.

Anthony Black, a Delta spokesman, said the “items” cited by the Transportation Department “are an isolated situation, which represent a tiny fraction of the passengers that we handle.”

Delta’s fine today follows one of $375,000 in July 2009 for similar infractions.

If an airline has sold more seats on a flight than are available, U.S. rules require that it seek volunteers willing to wait for another flight before removing, or “bumping,” passengers, according to the DOT. Passengers who are bumped are entitled to as much as $1,300 in compensation.

Delta classified some passengers it bumped as having willingly given up their seats, which undercut their right to compensation, the DOT said in its statement.