How to spell compound words in English? Not easy when there are three different options to choose from. It is a good idea to keep a good style guide nearby, but even then you may end up quite confused: "The AP Stylebook and Briefing on Media Law, a spiral-bound style manual produced by the world's leading news agency, is an essential handbook for all writers, editors, students and public relations specialists. The 2008 edition provides fundamental guidelines on spelling, grammar, punctuation and usage..."
http://www.ap.org/pages/product/order.html Why does AP write "stylebook" as one word and "style manual" with two?
Tour operator - written as two words - is probably the better option here, but isn't it a bit precious to enter a whole new answer to question the spelling of a word?