Several U.S. airlines are raising base roundtrip fares on domestic flights by $6, the first large-scale increase since June.

JPMorgan Chase analyst Jamie Baker says Delta Air Lines began boosting prices on Monday and was quickly matched by Southwest Airlines. Both airlines confirm the report. American, United, JetBlue and Virgin America also said on Tuesday that they matched the increase.

Baker says the hike covers corporate, leisure and deeply discounted fares.

The increase could be rolled back, but that’s unlikely with support from so many airlines. However, airlines constantly run sales and tinker with prices, reducing the effect of broad fare hikes.