ATLANTA — Delta and Northwest, seeking to combine to create the world's largest airline, posted losses yesterday totaling $10.5 billion for the first three months of the year, blamed on high fuel prices and write-downs of their companies' value.

The figures from Delta and Northwest follow large losses at other carriers, such as United Airlines' parent UAL Corp., which earlier this week reported a $537 million first-quarter loss on higher fuel costs, and likely rank among the industry's largest quarterly losses ever.

That red ink puts into focus the enormity of the challenge the industry faces to become profitable again amid $120-a-barrel oil — even with the benefits that consolidation can bring.

"All airlines are in the same boat," said Calyon Securities analyst Ray Neidl. "The industry cannot make money at the current ticket fare levels."

Atlanta-based Delta Air Lines Inc., the nation's third-largest carrier, said its loss widened in the first quarter to a whopping $6.39 billion. A few hours later, Northwest Airlines Corp. reported a $4.1 billion loss.