Washington (CNN) -- Airlines benefiting from a unplanned federal tax holiday should save the money for the government or pass it along to the passengers, but should not pocket the money themselves, key congressional leaders said Tuesday.

At issue is millions of dollars in passenger taxes -- taxes ordinarily collected by the airlines. But since Saturday, the airlines have not collected the taxes because of Congress's inability to pass a bill to fund the Federal Aviation Administration.

The airlines could have passed along the savings to air travelers. But instead, most airlines raised their base ticket prices at amounts equal to, or similar to, the expired tax.