An overview by Business Insider on how al-Shabaab simply "keeps on killing", which ends with:
Al Shabaab didn't just bomb a commercial plane. It might also have managed to smuggle an explosive device inside the most heavily guarded location in the entire country. If Shabaab was responsible for the suspected bomb attack, it would mark the first instance of the group detonating a bomb onboard a passenger plane. Like the other two attacks, it would be a gruesome sign of the group's resilience — and of its increasing danger years after the height of its territorial power.
Link:http://uk.businessinsider.com/shabaa...16-2?r=US&IR=T