This is book 1 in the trilogy called Up in the Air by R K Lilley. Bianca is a flight attendant in First Class along with her Best Friend Stephen.
This book contains lots of sexual content and is none the worse for it. Scenes with BDSM are written in a way that the story needs. This carries the feelings and back issues that Bianca and Mr Cavendish have. As the trilogy goes on a great love story unfolds along with great tension not just for Bianca and James Cavendish but for Stephen too.