Delta, Frontier, United, US Airways and Virgin America matched a Southwest-led roundtrip fare hike of $6 to $10,

which the carrier initiated Monday across the "bulk" of its network, according to FareCompare.com. "This increase attempt occurs on the heels of price hike momentum initiated last Thursday evening when JetBlue raised prices $10 roundtrip across their smaller route system with mixed legacy carrier matching over the weekend," according to a note from FareCompare.com CEO Rick Seaney.