Airline seatbelts are designed to restrain you from flying out of your seat in turbulence. They will do little to restrain your head from hitting the seat in front in a front-on impact, and have a good chance of causing injuries in any kind of impact. For that reason, if an impact is considered more likely than usual, you will be instructed to assume the brace position. (Note also that crew have proper harnesses.)

But those are lap belts, and also planes tend to have different issues than cars do.

if you're riding planes that are at risk of >50kph impacts, you should probably move to a different airline