US Airways and United Airlines are deep in merger discussions, the New York Times reported on Wednesday.
Such a deal would create one of the world's largest airlines.
US Airways shares were up about 26 percent at USD$8.61 after the closing bell. United's stock was up 8.2 percent at USD$20.51. Shares of other airlines also rose.
Any such deal is not expected to be announced for several weeks and talks could still fall apart, the newspaper reported, citing people briefed on the matter.
An alert posted on the newspaper's website said US Airways would be the acquirer, although an accompanying story made no such reference.
At a travel industry show in February, executives of US Airways and United said their companies were open to a merger.
"UAL has been supportive of consolidation for a long time," UAL Chief Financial Officer Kathryn Mikells said at the summit.
US Airways Chief Financial Officer Derek Kerr said in a separate interview that his airline was open to merging with another US carrier.
"Consolidation is one of the major ways this industry can become profitable," Kerr said.
The two carriers had come close to merging with each other in 2008, sources said at the time.