In 2017, a Challenger 604 business jet was passing under a much larger and heavier Airbus A380 over the Indian Ocean. The A380 was flying 1,000 feet above in the opposite direction. (This may seem dangerously close, but a separation of 1,000 feet is standard procedure.) The smaller jet rolled over at least three times, injuring several passengers. Its cabin looked like a bag of Halloween candy dumped out by a kid, and while it managed to make it safely to an emergency landing in Oman, it was written off. The G-forces it endured exceeded the structural limits of the aircraft.
What happened? Wake Turbulence. Pilots actively avoid situations like this one, and wake-turbulence incidents are very rare.
“Wake turbulence is pretty much exactly the same thing as happens in water when one boat passes through the wake of another, except that on water you can see the wake as waves. In the air you can’t see the wake. However, there is a clue where it might be, and that is to look for the vapor trail,”
Air Traffic Control uses tables published for wake vortex separation minima to keep aircraft a safe distance apart.
“These tables consider the size of both the preceding aircraft and the size of the following aircraft and give a safe distance in either miles or time depending upon the situation,” The A380 is given a spot all on its own in the tables, together with the Antonov An-225 cargo plane. Those two are so much bigger and heavier than anything else flying that they are referred to as “Super” by air traffic control, not just “Heavy.”
I hope this helped you understand wake turbulence.