A range of airlines are raising the prices on many domestic flights even though fuel prices are lower than normal, according to Reuters.

Recently, JetBlue Airways raised its fares by $4 per round trip, or $2 per one-way, on a small number of routes in order to match the industry increase, Reuters reported. Oil prices have fallen by about one-fifth since late April.

Airlines are hiking prices even though gas prices are on the decline, suggesting that airlines do not intend to pass along savings from the decline in jet fuel prices to their customers, Reuters reported.

Southwest Airlines matched it a day later, leading other airlines to follow suit, according to Reuters. Southwest carries the most domestic passengers, so other airlines usually wait until Southwest makes the move.

A JetBlue spokeswoman confirmed the increase on its domestic flights, and Delta said it had matched and expanded "an industry increase," Reuters reported. United Airlines and American Airlines, which also owns US Airways, confirmed matching the $4 increase, too.

"We matched an industry increase and expanded it to additional markets," Delta spokesman Anthony Black said, according to Reuters.

The last successful broad increase occurred in April, but higher fares don't always result in passengers paying more because airlines run frequent sales, and they adjust fares on individual flights depending on demand, according to Reuters.

The Ebola outbreak scare does not seem to have placed a damper on travel demand, Reuters reported.