KLM is the Dutch airline that evolved its use of Twitter in unexpected ways. They originally used twitter as a platform for social media marketing. They quickly realized that it could also be used as a platform for communicating service disruptions. This proved invaluable during the 2011 Iceland volcano eruption.
From a communications platform, KLM came to rely on Twitter as a customer interaction portal as well. Their Twitter page evolved into a potent “Lost and Found” system to help return items to its passengers.
You see, passengers that exited through airport security were not allowed to go back in to get their left-behind luggages. But KLM employees could go and deliver these to customers. So the twitter platform was used to help call KLM staff for help with lost or left behind luggages!
Source: The Technology Fallacy
Other KLM twitter campaigns were discussed here: