DALLAS » American Airlines is raising mainland round-trip base fares to Hawaii and Canada by up to $21, and other U.S. base fares $10 per round trip.

If the increase sticks, it would be the seventh broad price increase this year by U.S. airlines, which say they need more revenue to offset rising fuel prices.

American Airlines spokesman Tim Smith confirmed that the airline raised prices Wednesday night. Delta said it was studying the move but had not matched American yet.

United, Continental, US Airways and two low-cost carriers, JetBlue Airways and AirTran Airways, said they had not raised prices. Southwest did not immediately comment.

Airlines are also boosting fees. In the last two weeks, JetBlue raised the charge for checking a second bag to $35 from $30, and American upped the cost of making a flight reservation by phone to $25 from $20.

The Consumer Travel Alliance said yesterday that passengers paid U.S. airlines more than $9.2 billion in fees last year — an average of $36.80 per round trip — and many of the charges weren’t disclosed to passengers when they bought their tickets.

The frequent fare increases so far in 2011 are reminiscent of 2008, when airlines raised many to keep up with skyrocketing fuel costs.

Rick Seaney, CEO of travel website FareCompare.com, said if the pattern of 2008 holds, the airlines might attempt weekly raises through the end of April.

In most cases this year, the five so-called network airlines — United, Continental, Delta, American and US Airways — have quickly matched each other’s price increases. Low-cost airlines have sometimes balked, which forces the network companies to scale back prices on routes where they compete with them.

Southwest CEO Gary Kelly said this week that fare increases aren’t keeping up with fuel prices, and he’s not afraid that higher fares will drive passengers away. He noted that even after several fare increases, Southwest’s February traffic rose 13 percent over the same month last year.

Kelly said Southwest is on pace to spend $1.3 billion more on fuel than in 2010, when its bill came to $3.6 billion. That was 33 percent of all costs, just behind labor as Southwest’s top expense.