Airfares going up another $10

NEW YORK (CNNMoney) -- Airfares are going up yet again.

Late Tuesday, Southwest Airlines raised all of its round-trip fares by $10. Delta (DAL, Fortune 500) initiated this latest round of price increases on Monday, and as of midday Wednesday American Airlines (AMR, Fortune 500), JetBlue (JBLU) and United Airlines (UAL) had matched it.

Industry experts say the $10 increase is likely to be adopted industrywide.

If so, this would mark the seventh time this year that domestic airlines have jacked up fares.

In the past five years, no industrywide attempt to raise fares failed when Southwest was on-board.

Southwest (LUV, Fortune 500) blames the price of fuel.

"This higher fare is to offset higher fuel costs that we continue to face in the industry," said company spokeswoman Laurel Moffat.

This year is similar to 2008, when oil prices were surging and oil hit a record high of $145 a barrel. In 2008, there were 17 successful hikes.

Oil was trading at about $111 a barrel on Wednesday.

Rick Seaney, CEO of FareCompare.com, said the industry is "on pace to break that record this year," though he believes prices won't go too high.

"In 2007, it was not unusual to have one-third of a plane empty," Seaney said. "Today to keep revenues up, planes have to be full. And to fill up those planes, you have to be price conscious. So prices can't get too out of whack."

When airlines announce these price increases, they are doing two things: gauging consumer appetite and the willingness of competitors to follow. Airlines are only able to charge higher prices if customers are willing to pay. And, these hikes aren't successful unless most or all competitors match the hike.

If only one airline announces a hike, it will end up on the last few pages on airline ticket comparison sites -- effectively out of view for many online shoppers.

Industry experts believe that fliers will see more airfare hikes throughout the year. Seaney said it wouldn't surprise him if we saw one a week for the next month.

And with the summer travel season right around the corner, consumers can expect even higher airline prices.

Between June 9 and Aug. 21, airlines are charging additional summer premiums. Last year was the first year that airlines started charging summer premiums.

Demand is typically higher at this time or year, so airlines are able to charge more.