NEW YORK (CNN) - Southwest Airlines is joining several of its rivals in passing along higher fuel costs to customers, but is not adding as much to ticket costs as other airlines have.

Southwest (Research) said it is raising fares $1 to $3 each way using a mileage-based pricing approach, a spokesman said Monday. Flights of less than 600 miles now cost $1 more, flights 600 to 900 miles cost $2 more and flights over 900 miles have gone up by $3.

The move by Southwest follows a recent fare increase by Northwest Airlines, its second in as many months.

Last week, Northwest raised one-way prices $5 for flights of less than 1,000 miles and $10 for flights more than 1,000 miles.

Continental (Research) and America West (Research) matched Northwest's (Research) first increase in late February.

Rising crude oil prices are driving up the cost of jet fuel. The price of light sweet crude has risen about 16 percent in the past four months, and the government and OPEC have both warned of higher gasoline prices in coming months.