[tripoli]

Does happen in the military more than you would think. Its is an automatic ticket to retirement. Usually, a military pilot that does so will be presented with the option to retire immediately while still looking over the jet on the runway. If it is a mechanical problem, its not such an issue, otherwise, you have just lost your career, which is enough of an issue to make most not forget to extend the gear.

For civilian, generally, you will get a 6 month suspension of your license. You will also get a check ride with an FAA instructor to insure when you do get back in the cockpit, you know all your procedures. Generally, the cost of insurance and repair is enough to keep most general aviation pilots on their toes with the added threat of the embarrassment of having a gear up landing on their records.