I did last minute midnight packing and put the top line D lock in my carry-on for a flight within Europe. But it was rejected at security. They said it can be used as a weapon. But then I pointed out that the laptop bag is just as heavy and can also be swung with the same momentum and impact. They asked me if I wanted to check it in and I said yes, but they carried it over to the trash bin and was going to drop it in so I insisted again and they give it back to me.

I had to go to the checked baggage counter again and pay extra. I asked the lady if I could stick it into the bike box that I had just checked in 5 minutes ago, since normally I see them at other airports put to the side waiting for more oversized baggage to be taken together at one time. She said it wasn't possible but I don't know if she confused what I meant with the normal size baggage that goes through the automated system.

I put the D lock in my shopping bag to check in as an additional item, but she said it was too light and asked me to add more so that it's at least 5 kg. But I didn't have much else and could only get up to 3 kg. I'm assuming that a light bag may encounter problems with the sorting machines or belt system. I was worried about it getting lost but it arrived at the destination.

Anyway, not acting on my split second of hesitation when I put the D lock into my carry-on wasted some money.

I had never heard that you can't carry that type of lock in a carry on bag. Thank you for warning us.

This has happened to me on multiple occasions in multiple parts of the world. Always check locks, pumps, tools.

Security at Paris-Orly wouldn't let me bring a selection of unusual French cheeses in my carry-on daypack on a flight to Germany. They were intended as a gift to my cheese-loving German friends I was going to visit. Airport security claimed the moisture content of the cheese was high enough that it could be an explosive rather than actual cheese. I never would have expected this response in cheese-obsessed France. I returned to the counter and they gave me a small box for the cheese in order to check it. The airline then proceeded to lose the box and I never saw it again.

I was once on a flight to Quito, Ecuador, and some idiot sitting near me was using highly flammable nail polish remover during the flight. That stuff should have never made it on the flight. At least a flight attendant told the woman to close the bottle and keep it closed until she exits the plane.

I took a 4 inch folding knife onto the airplane at Rome Ciampino and security either didn't see it or saw it and didn't care.

There are extremes on both ends. Air travel security is a joke.

^^^ This

I think thats obvious.

When I flew out of the Saigon airport over a decade ago, they confiscated (very respectfully) my eating fork! Go figure.