This was the deadline for the Entry/Exit System or EES, to be active at every Schengen border crossing point in all 29 participating countries. The system began being gradually introduced from October to strengthen security and ultimately make travel smoother, though due to some hiccups, not every point will be fully rolling it out. There have been long queues at some European airports and warnings that delays could be worse during busy holiday periods. EES is a digital system designed to keep track of when non-EU citizens - including those from the UK - enter and leave the Schengen Area. This covers 29 European countries - mainly in the EU - which people can travel across without border controls. It includes many popular destinations for UK travellers, such as France, Spain, Portugal, Italy and Greece. Under the new system, fingerprints and a photo have to be registered. EES will eventually replace the current system of passports being stamped by a border officer. (BBC)