In the days when gas cost 25 cents a gallon, it was an easy decision which was the cheaper method of travel, flying or driving. Driving was the standard mode of transportation, and flying was a luxury. However, with airlines in a cutthroat competition for customers, and gasoline becoming increasingly expensive, this may no longer hold true under all circumstances. The economy of both options should be evaluated for each planned trip. Don't assume that flying is the most expensive option, especially if you use the following tips to get the cheapest fares.

In order to figure out how much gas you'll need to reach your destination, find out the mileage both ways and then use an online fuel consumption calculator. Of course, how much gas you will use depends on whether you drive a Hummer or a Kia. For long trips, add on some money for wear and tear on your car and the tires.

In addition, add up the costs of food and beverages consumed en route, as well as hotel costs if the car trip lasts more than one day. Hotel costs alone can add up to a few hundred dollars for a two-way trip, and since cross-country airfares can be less than five hundred dollars, this expense alone may make it cheaper to fly. If you are travelling with a family, the hotel bill stays relatively constant while the airfare per person adds up quickly. However, for a single person or even a couple, air fare may very well be comparable.

Check out airfares with at least three online travel agencies. You will find a wide difference in fares, because each agency may have different specials, and charge different service fees.

When planning your trip, book as far in advance as possible. Economy seats on desirable flights sell out fast, especially during peak season. If possible, book your air travel during the off season, and avoid travelling at Christmas and New Years, spring break and the summer vacation season from July to August.

Airfare specials are often offered in spring and fall, making flying much more economical.

Students or a seniors should inquire for special rates. Airlines give student discounts, and seniors may be able to get a good deal on airfare from the AARP. If you belong to a club or service organization, ask if they are affiliated with any airlines or have a discount travel program.

If you are travelling in a large group and are contemplating using individual cars or a long bus ride, check the cost of charter aircraft. Sometimes it is cheaper to reserve an entire plane than buy individual tickets. It's a lot more pleasant to take a short plane trip together than sit for an entire day stuffed together in a vehicle.

Last but not least, consider how much time you will save by flying. If you only have a week or two for your vacation, driving may cut into your free time significantly. It's tiring, too, and you may need a day or two to recuperate after a day of driving. It may be worth a bit of extra money to save a lot of aggravation.

Airfares out of large airports can be more expensive than out of smaller municipal airports, so if you are travelling to a large city, check smaller airports nearby. The trip may be much cheaper with only a small detour. Be sure to consider cab fare or rental car rates to get to final destination.