The International Rosetta Mission, a cornerstone mission of the European Space Agency Scientific Programme, was launched on 2nd March 2004 on its 10 years journey towards a rendezvous with comet Churyumov Gerasimenko. Once reached the comet nucleus in summer 2014, Rosetta will orbit it for about 1.5 years down to distances of a few kilometers and deliver a Lander, named Philae, onto its surface. In its first year of flight, the spacecraft and its payloads have gone through an extensive commissioning exercise, several trajectory correction manoeuvres, the first Earth gravity assist manoeuvre (1 year after launch), and some important scientific operations. The spacecraft has finally entered its first Passive Cruise phase end of July 2005. This paper describes the mission operations experiences collected during the first year of routine flight, after completion of the commissioning activities mid-October 2004. The two main mission events that occurred during this period are described: the first Earth swing-by in March 2005 and the scientific Deep Impact observation campaign in July 2005. An overview of the major in-flight anomalies is given and lessons learnt are presented.