Virgin Airlines

Alaska Airlines parent company Alaska Air Group said on April 4 it was acquiring Virgin America in a friendly takeover worth around $4 billion including debt to create the U.S.'s fifth-largest airline.

A definitive merger agreement had been unanimously approved by the boards of both companies, it said in a statement.

Virgin Galactic "ignored" repeated warnings in the years leading up to the deadly crash of its spacecraft in California, a rocket science safety expert said Sunday, as investigators hunted for clues to the accident.