United Airlines is attempting an airfare hike of up to $20 round-trip on domestic tickets. This is the carrier's second push for a fare increase this month.
Airfare tracking website FareCompare.com reported the increase Wednesday, noting the higher prices are based on distance, with shorter trips going up $4 and longer distance routes increasing by $20 round-trip.
As of Thursday, JetBlue is the only airline to match United's increase, Rick Seaney, chief executive of FareCompare.com, said.
But even if United's current price hike fails to stick, airfares are still forecast to rise throughout the year. Airlines are paring seats to match demand. (Read more: Five Trends to Look for in Travel This Year)
JPMorgan analyst Jamie Baker said he expects other airlines to match United's second fare increase, but Southwest Airlines' support would be needed for the price hike to stick, The Associated Press reported.
Southwest carries more passengers within the U.S. than any airline and wields great influence over prices on many routes, according to the AP.
United attempted a similar fare increase on January 3, but retreated after some airlines failed to match the hike, including Southwest.
The Associated Press contributed to this report.