The early personal flight sims were marketed primarily as games: screen graphics were simple, and the demands on the low-powered computers of the time were slight. All that has changed. Now there are many fully-featured airplane simulator programs available.

The in-flight graphics of today's programs are almost astounding when compared with the first airplane simulators for personal computers. But all those graphics and quick responses to control inputs exact a toll on computer resources. Here are three critical things to check before plunking down your cash for a flight simulator.

1: Computing power. Will the simulator match your computer system's specs? Most computer games make heavy demands on the amount and speed of a computer's random access memory, or RAM, and flight simulators are no exception. Plus, many of today's flight sims require lightning fast video cards that have their own collection of memory. As you can imagine, a graphics-heavy simulation that is moving quickly across your monitor demands a lot more of a video card than does a simulation of a piece of paper in a word-processing program, or a grouping of cells on a simple spreadsheet.

Seasoned gamers tend to invest a fair amount of money in their computers, with high-end video cards, lots of RAM, hard disk drives that can read and write information rapidly, high-definition monitors, speaker systems, and much more. But even when armed with fast hardware built expressly for gaming, some flight sim aficionados have been disappointed by the slow frame rates (the speeds at which graphics are refreshed) and the load times for the latest versions of Flight Simulator and other popular programs.

Before you buy a flight sim package, make sure you carefully investigate the requirements for the software. A flight simulator that advances in uneven jumps, or just freezes when too many demands are made on the computer's processor chip or video card RAM, can be a discouraging flight sim event.

2: Expandability. Is the simulator expandable for external controls? Just about any flight simulator on the market today comes ready-to-fly out of the box using a system of keyboard controls. For example, the up arrow pulls the nose of the aircraft up; pushing the down arrow reverses the yoke pressure. But, of course, pilots don't control airplanes with computer keyboards.

If you become a flight simulator enthusiast, you're going to want to control the simulator with more realistic inputs. Make sure that the flight sim you're considering will accommodate a number of control inputs, such as joysticks, yokes, throttle controls, and rudder pedals. Many of the controls marketed today come with USB inputs, but some flight simulators can still provide a struggle for configuring a specific control device. Check to see if the manufacturer recommends a certain brand or model of control input before you buy the software.

3: Regular software updates. Are updates available for the software? Make sure that you're not purchasing a flight simulator package that has been dropped by the software manufacturer. There should be updates of new scenery packages, additional, and other features such as air traffic control voicing and weather phenomena. For example, airplane simulator enthusiasts have been waiting for the next release of Microsoft Flight Simulator for more than four years. And that release may be a long time coming, because Microsoft did away with the product's development team in 2009. If you experience problems with a flight simulator package that turns out to be orphaned, you may not have any support group to turn to.

An airplane simulator can be a good source of flying knowledge. Flight simulators can provide hours of fun, learning to fly your own aircraft from the comfort of your own home. Investigate the various packages available, compare the features of realism, and benefits such as being able to load the program on more than one computer, and definitely check the technical requirements.

With the right flight sim software that matches your computer's performance, you'll be off the runway and bound for the wild blue yonder, and at a much lower cost than even a single hour in a real training airplane.