O'Brien had been in the post for almost a year, having survived a marketing department cull last January. She replaced Jill McDonald, who was made redundant alongside head of sales and marketing for UK & Ireland Alan Burnett. O'Brien was promoted to the role from her position as UK & Ireland marketing director.
At US-owned Regus, she will be responsible for a UK media budget of less than £500,000, according to Nielsen Media
Research, compared with BA's £23m spend. The Regus network spans 60 countries and has 700 business centres. In 2005 the company, which was established in 1989, had revenue of £463m.
A spokeswoman for BA confirmed that the carrier will now begin a recruitment process to find a replacement for O'Brien, who leaves in March.
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the .