A lavatory can be defined as one of three things:
- A room equipped with washing and often toilet facilities; a bathroom.
- A washbowl or basin, especially one permanently installed with running water.
- A flush toilet.
As per regulations set for by the United States government every commercial airliner must have a lavatory on board. This is of great benefit to the passengers because who wants to be trapped on an airplane for a commute and not be able to go to the bathroom. On the ground all buildings whether for commercial or private use must be equipped with at least one bathroom and one source of running water. However, in general aviation often the planes are way to small and only carry 1 to 4 people so a bathroom is not necessary. Not to mention that in general aviation the flights are usually much shorter and the distances flow are not as great as airliners so the need for a lavatory is much less.
In the charter industry, it is in the best interest of the charter company to equip their aircraft with lavatories. Charter customers spend decent money to fly in a jet that has the best comfort, convenience, and features. Flying in a charter jet compared to flying first class in an airliner is like riding in a BMW compared to a limousine. Both are real comfortable, both have great features, but the BMW is personal and the limousine is a group ride. If you are going to rent a charter jet then you should have all the comfort and convenience of a first class ride on an airliner with the privacy of your own bedroom.