AAFA Multi-Engine Program
If your goal is to someday fly for a major airline, you will need to obtain a multi-engine rating. Most airlines require their applicants to have at least 100 hours of multi-engine time. The multi-engine rating allows you be pilot-in-command in a complex multi-engine aircraft.
Even if you do not make a career out of flying, multi-engine aircraft allow you to fly higher, farther, and faster with a greater measure of safety. To add a multi-engine rating to your private or commercial license, the FAA requires an instructor endorsement and a practical test. There is no written exam required for the multi-engine rating.