I'm sure everybody will see it on the TV but here is the info anyway.
It seems that a terrorist plot to blow up trans-atlantic flights in the air has been foiled. It seems that this was going to be done using liquid explosives.
The UK police/security services have arrested 25 people, 21 of whom remain in custody. The terrorists are believed to have been born in the UK.
There are special security measures being taken at UK and US airports. Almost no hand luggage is being allowed. Only basically wallet and travel documents. The US has specifically banned passengers from carrying any liquid onto flights (with a few exceptions - baby milk etc which will have to be proven safe by drinking some).
There is still not much info at the moment though. Check http://www.bbc.co.uk/news for the latest throughout the day.