When we start skydiving we are all taught to check our gear at the start of each day, and before every jump, at the flightline. What happens is that, once we become experienced skydivers, we can totally forget about this basic principle and cause potentially fatal problems, such as these incidents below..
The 3-ring loop shown above is frayed and on the verge of breaking. This was spotted by an observant friend– in the aircraft on the climb to altitude! The owner of the gear elected to ride down in the aircraft rather than risk the loop breaking on opening or during the canopy flight. Note that the worn loop in question is on the RSL side of the riser. If the loop had broken on deployment, the RSL would deploy the reserve canopy, which would probably entangle the reserve with the main, as the opposite main riser would be still attached to the harness.
The jumper in the video below left the aircraft with his chest strap not fastened. Thanks to cameraman Andrey Veselov's intervention, all ended well.
A flightline check would have prevented both incidents. There seems to be a big variance in the amount of gear checks being made in different places around the world. In the UK every load has a flightline checklist, where each person on the load is initialed by the checking jumper. It's a good policy, adopted in many but not all countries.
Flightline checks are for both student and experienced jumpers, they are one of the easiest steps to keep you and jumpers around you safe. They don't take long, have never killed anyone, and have saved countless lives.