United Airlines has decided to charge an extra fee for the extra luggage checked in, with the second bag costing $25 more. This new checked bag policy will be effective from May 5, 2008.

United Airlines has become the first big carrier to impose a fee for a service that has long been included in the price of a ticket i.e. it will begin charging some passengers $50 to check in a second piece of luggage on domestic round-trip flights.

United said that, it won’t affect many fliers as a research into passengers' habits has determined that only one in four check in more than one bag. By charging the 25% of people who check in more than one bag, the weight of the airplane can be brought down and at the same time fares can be kept low.

The main reason for this is the rising jet fuel prices. The airlines neither want to increase the fares of the tickets nor deduct the salary of their employees. So, they are coming up with alternate measures to compensate the everyday decreasing revenues.

The fee of $25 for the second bag each way is expected to generate more than $100 million of revenue. In addition, United expects fewer checked bags as a result of the fee, which could lower fuel expenses.

In the quarter that ended on Dec. 31, UAL Corp.’s fuel costs increased by $359 million, or 25%, from the last year’s figures.

"The airlines are looking for every possible revenue source they can find and still cut fares without cutting wages, because right now they can't go any lower," said Airline consultant Terry Trippler of Trippler Associates.

The initial public response to this move to this response has not been bad. People don’t mind giving few extra dollars unless the ticket fares stay low. Tom Parsons, chief executive of the travel Web site Bestfares.com said that people shouldn't be upset, because they still want to fly coast to coast for $199.

The other airlines have not still decided whether or not they are going to implement such measures. But experts believe that they will be watching the results of the step taken by United Airlines and will surely scrap the two-free-bag rule, similar to the other amenities such as free meals and pillows which were taken off.

``Others will watch and see how it works for United,'' said Daniel Kasper, a managing director of consulting group LECG Corp. “Their response will determine whether it sticks,'' he added.

United Airlines also announced that it will be charging a flat rate of $100 each for all the customers checking in up to four additional bags. Previously, the airline charged in a range of $85 to $125 a bag.

Smaller airlines have already been charging the passengers for checking in more than one piece of luggage. A low-cost carrier, Spirit Airlines, charges $10 each for the first two bags.

UAL's shares plunged to $39.15, a decrease of 4.7% which is in line with weakness across most of the airline sector.