It was announced this week that the US has banned any electronic devices larger than a mobile phone from carry-on baggage from some Middle Eastern gateways. The same holds true internationally with regards to power banks. Sometimes power banks can only be in checked luggage, sometimes it's only permitted in carry-on, so make sure you ask before checking your bags. I've been escorted to my bag to take a power bank out or have had it taken away at security. Apparently it depends on the wattage of the power bank, so have it ready with you when you check-in and ask the gate agent so you don't end up having it taken. There's also inconsistency on whether it needs to be removed in security, so make sure you read the signs. My favorite one is this one.