Representatives from auto companies and the U.S. postal service meet in Washington D.C. on Wednesday to discuss replacing the postal service’s fleet of mail trucks.

The trucks, manufactured by a fighter jet maker, were designed to last but not for 30 years. They are guzzling fuel, are requiring too much maintenance, and aren’t big enough for the postal service’s growing e-commerce package business.

The contract for a new fleet of trucks could be a $6 billion bonanza for the winning manufacturer, but it also has its challenges.

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