Earlier this week, Delta started the latest round of price increases by adding $10 to each round-trip ticket.
Southwest Airlines followed with a price hike of $5 on all of its each-way tickets.
On Wednesday, American, United and Jetblue matched the $10 increase on round-trip flights.
Airlines insist they need higher fares to cover the rising costs of jet fuel. Oil is now above $110 per barrel, having risen 21 percent this year.
The Associated Press contributed to this story.
