Some MMOGs have been designed to accurately simulate certain aspects of the real world. They tend to be very specific to industries or activities of very large risk and huge potential loss, such as rocket science, airplanes, trucks, battle tanks, submarines etc. Gradually as simulation technology is getting more mainstream, so too various simulators arrive into more mundane industries.
The initial goal of World War II Online was to create a map (in north western Europe) that had real world physics (gravity, air/water resistance, etc.), and ability for players to have some strategic abilities to its basic FPS/RPG role. While the current version is not quite a true simulated world, it is very complex and contains a large persistent world.
The MMOG genre of air traffic simulation is one example, with networks such as VATSIM and IVAO striving to provide rigorously authentic flight-simulation environments to players in both pilot and air traffic controller roles. In this category of MMOGs, the objective is to create duplicates of the real world for people who cannot or do not wish to undertake those experiences in real life. For example, flight simulation via an MMOG requires far less expenditure of time and money, is completely risk-free, and is far less restrictive (fewer regulations to adhere to, no medical exams to pass, and so on).
Another specialist area is mobile telecoms operator (carrier) business where billion-dollar investments in networks are needed but marketshares are won and lost on issues from segmentation to handset subsidies. A specialist simulation was developed by Nokia called Equilibrium/Arbitrage to have over a two-day period five teams of top management of one operator/carrier play a "wargame" against each other, under extremely realistic conditions, with one operator an incumbent fixed and mobile network operator, another a new entrant mobile operator, a third a fixed-line/internet operator etc. Each team is measured by outperforming their rivals by market expectations of that type of player. Thus each player has drastically different goals, but within the simulation, any one team can win. Also to ensure maximum intensity, only one team can win. Telecoms senior executives who have taken the Equilibrium/Arbitrage simulation say it is the most intense, and most useful training they have ever experienced. It is typical of business use of simulators, in very senior management training/retraining.
Other online simulation games include War Thunder, Motor City Online, The Sims Online, and Jumpgate.