people started clapping just after we landed

[MNBluestater]

Hmmm, if you loosen the fastened belt and turn it over

Originally Posted by DingerX

. Non functioning seat belts was the most common, on the occasions when there were cabin crew (sometimes there were none) they just told you to tie the belt in a knot if the buckle wasn't there or didn't work.

Heck, I saw that happen in the min-nineties (97 to be exact), on a Tower Air flight (JFK-ORY) during their brief run at trying to be a regularly-scheduled airline.
Seatbelt of the guy next to me was installed backwards. On popping the cushion, we found that a pin was installed to prevent seatbelt from "deplaning" -- so we couldn't fix it. Called the FA over,

"It's your seat, sit in it"

Interestingly, the aircraft never got above FL220, and there was no applause on landing (but plenty of relief).

Voila, the buckle is on the top !!! And if you tighten a little, it will hold you in just fine...

That's what I assume you meant by "installed backwards" that the buckle faced down...this would not be a situation to keep an aircraft from taking off...