US Airways initiated the fare increase late Thursday on most routes. Delta Air Lines later followed. No other airlines had joined in as of Friday morning.

This is the tenth time this year airlines have tried widespread price increases. Six of the previous nine stuck. The last three failed within days because other airlines didn’t raise prices too.

Oil is now above $110 per barrel, having risen 21 percent so far this year. Fare watcher Rick Seaney points out that the airlines successfully raised prices four times in April 2008 when oil prices rose from $102 to $117.