Most virtual aviators use one of two simulator software programs, Microsoft’s FSX or Laminar Research’s X-Plane, which interface with communication and tracking software usually provided free by one of the virtual flying networks. Within the last decade, a thriving market for so-called add-on software compatible with FSX and X-Plane has emerged. One of the most successful manufacturers is PMDG, which produces stunningly realistic add-ons that put users in the cockpits of aircraft like Boeing’s 737 and 777. All the switches and knobs you see on the screen are what you would see in the actual planes, and the programs come with Boeing manuals to help you figure out what’s what.

In a post on PMDG’s online forum, the company’s chief executive, Robert Randazzo, a former airline captain, confirmed that Captain Shah had purchased PMDG’s 777 add-on, the same type of aircraft he flew for Malaysia Airlines. He also noted, “Captain Shah was well known to many in the flight simulation community because he had developed an online presence in which he dedicated many hours of his time to promoting the enjoyment of flying generally, and flight simulation specifically.”

Hardware can be equally sophisticated with full instrument panels, radios, throttle quadrants, yokes and rudder pedals. Companies like Redbird Flight Simulations and Virtual Fly sell all-in-one units with full motion that cost up to $60,000.

Pete Wright, 44, a software developer in Deltona, Fla., who reviews add-ons for PC Pilot Magazine, flies a home-built rig that includes a yoke, rudder pedals, a full switch panel and levers for throttle, spoilers, flaps and reversers. He also has three HD video screens hooked up to an infrared sensor that tracks his head movements so when he looks back and forth the view out of his virtual aircraft changes accordingly.

The setup, plus software, cost more than $10,000 — more than it would cost to get a real private pilot’s license. “But I can stay at home in my cockpit and fly any aircraft you care to name, anywhere in the world,” said Mr. Wright, who has more than 12,000 hours of virtual flight time and does demonstrations in his simulator for viewers of his YouTube channel, FroogleSim.

Still, real pilots will tell you that nothing compares to actual flight. Simulators can be fantastic training devices. But they can’t replicate the feel of the controls in a real airplane or the dynamic conditions of flight. It’s a fact some virtual enthusiasts resist but most concede.

Mr. Friedland of Vatsim said that despite his many simulated flights over all kinds of terrain and in all kinds of weather conditions, “I would no more try to do any of that in a real airplane than I would try to climb Everest without supplemental oxygen or Sherpas.”