United has increased its fees for checked bags, following a precedent set by JetBlue. 

The first checked bag on domestic flights and flights between the U.S. and Canada, Mexico and the rest of the Americas jumped from $25 to $30 on Friday. 

United also upped the cost for a second checked bag from $35 to $40, though flyers between the U.S. and Mexico continue to pay $35. 

"As we continue to make investments that make travel on United better, we are making adjustments to our checked bag fees in select markets -- most of which have not been changed in eight years. These changes allow us to continue investing in the overall customer experience in today's marketplace," the company said.

JetBlue on Monday raised its fee for the first checked bag from the longtime industry standard of $25 to $30. 

Carriers are currently seeing profit margins squeezed by higher fuel costs and stagnant airfares.

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